Plenty of places take their name from a visual resemblance to something else. Boat Rock, Whithorn is “shaped nearly like a boat” and Maidenpap, Kirkgunzeon “derives its name from its protuberant shape somewhat resembling a female breast.” There’s a sweet spot, somewhere between rock and hill, where the outlines of these names stand out clearly on the map. I’ve found 37 so far, with ‘fiddle’ being the most common shape. [I’ve taken ‘square’ to be a noun like ‘diamond’ rather than an adjective like ’round’ or ‘long’.] Here are the numbers so far:
Fiddle 7 Square 4 Halfmoon 3 Horseshoe 2 Punch Bowl 2 Spectacle 2 Ace of Clubs 1 Axe 1 Bessie’s Apron 1 Cocked Hat 1 Crows Nest 1 Diamond 1 Dragon’s Eye 1 Float Cock 1 Gun 1 Jib 1 Quarter Cake 1 Roundhead 1 Sand Glass 1 Scythe 1 T. 1 Triangle 1 Trump 1
Ace of Clubs Plantation, Kirkcolm WIG NX 032 698
There is no plantation here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Axe Wood, Closeburn DMF NX 906 891
This wood has the same shape on the OS 1st ed six-inch, but is unnamed.

Reproduced with the permission of the National Library of Scotland
Bessie’s Apron Plantation, Hoddom DMF NY 180 779
There is no plantation here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Cocked Hat Plantation, Troqueer KCB NX 933 737
“A small plantation on the lands of Golielea, its wood consists chiefly of oak. It had formerly been the form of a cocked hat hence the name.” OS1/20/70/3
“A small plantation on the lands of Goldielea consisting of oak trees this plantation has been planted on the site of a former one – which had been planted by Colonel Maxwell – its shape was that of the figure of a cocked hat hence the name.” OS1/20/70/52

Reproduced with the permission of the National Library of Scotland
Crows’ Nest Plantation, Kirkgunzeon KCB NX 870 630
The OS Name Book attributes this name to nesting crows. I think it’s at least as likely that the plantation was named after its shape.
“A small circular plantation on the farm of Bargrug, its wood consists of Fir. The origin of its name is from a few Crows having their nests on it ann[ually]” OS1/20/115/10

Reproduced with the permission of the National Library of Scotland
Diamond Plantation, Balmaghie KCB NX 657 648
“A mixed plantation (chiefly fir) upon the summit of Milntack Hill. It takes its name from being Diamond shaped.” OS1/20/107/8 (see also OS1/20/106/15 & OS1/20/106/32)

Reproduced with the permission of the National Library of Scotland
Dragon’s Eye Wood, DMF NY 312 769
This name appears on the most recent OS map. It appears to be fairly recent as it isn’t marked on any of the maps hosted on the NLS website. The ‘dragon’s eye’ is a small pool with an island (presumably the dragon’s pupil) in the middle.
Fiddle Plantation, Kirkmichael DMF NX 996 894
The most fiddle-like of the seven fiddle-names in this list.
“A small fir plantation in the form of a fiddle…” OS1/10/32/95

Reproduced with the permission of the National Library of Scotland
Fiddle Plantation, Wamphray DMF NY 133 948
“A wood of spruce fir of about 30 years growth. It is situate on the Eastern slope of Bl[aze] Hill and was so called from its being shaped somewhat like [a] fiddle. Not known, consequently expunged being so insignificant.” OS1/10/50/160 OS1/10/50/160

Reproduced with the permission of the National Library of Scotland
Fiddle Plantation, Girthon KCB NX 599 545
The OS 1st ed six-inch map shows a fairly indistinct, unhained group of trees. The shape is much more cleary marked on the 2nd ed, below.
“A small clump of trees in Cally demesne, situated nearly in the centre of “Deer Park”” “OS1/20/128/96

Reproduced with the permission of the National Library of Scotland
Fiddle Plantation, Hutton & Corrie DMF NY 171 925
There is no plantation here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Fiddle Wood, Lochmaben DMF NY 067 798
There is no wood here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Fiddle Wood, Urr KCB NX 821 707
This wood is marked on the OS 1st ed six-inch but is unnamed.

Reproduced with the permission of the National Library of Scotland
Fiddle Wood, Penninghame WIG NX 373 683
This wood is marked on the OS six-inch 1st ed as The Green Knowes Plantation, after the adjacent The Green Knowes.
“A small plantation of fir & forest trees.” OS1/35/14/15
“A small plantation of fir trees with some ash, oak & elm mixed It is 1/2 a mile E. of Glenrazie farm house.” OS1/35/14/33

Reproduced with the permission of the National Library of Scotland
Float Cock Island, Kelton KCB NX 734 607
“A small island in the River Dee at the south side of Lodge Island.” OS1/20/112/19

Reproduced with the permission of the National Library of Scotland
Gun Wood, Anwoth KCB NX 584 593
This area is marked out, with a few trees at the very east, on the 1st ed. six-inch OS but is unnamed.

Reproduced with the permission of the National Library of Scotland
Halfmoon Plantation, St Mungo DMF NY 140 790
There is no wood here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Halfmoon Plantation, Sorbie WIG NX 468 464
“A portion of mixed wood upon the farm of Millisle & estate of the Earl of Galloway” OS1/35/78/5

Reproduced with the permission of the National Library of Scotland
Half Moon, Glasserton WIG NX 432 287
This half-moon-shaped section of Enoch Plantation is marked as Half Moon on the current OS.

Reproduced with the permission of the National Library of Scotland
Horseshoe Plantation, Morton DMF NX 888 958
This plantation is marked on the 1st ed. six-inch OS but is unnamed. Both this and Horseshoe Plantation, Kirkconnel (below) are shaped – to my eye – like horse hooves rather than shoes. Horseshoe Plantation, Caddonfoot SLK (NT 439 332) is laid out in classic horseshoe shape.

Reproduced with the permission of the National Library of Scotland
Horseshoe Plantation, Kirkconnel DMF NS 724 143
There is no plantation here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Jib, Kirkmaiden WIG NX 097 399
“This name applies to a triangular piece of land held as a small farm or croft by William Corkran, The property of Colonel McDowall of Logan. Lies midway between Clash Hill and Muldaddie Hill.” OS1/35/82/3
I assume the reference here is to JIB ‘a triangular sail’. However, it’s worth noting that Scots JIB is ‘a protective leather covering for a stone-mason’s left thumb, used to prevent chafing by the chisel [from its triangular shape, like a jib-sail.]’ JIB in DSL
27/06/21: Carole Hough (2001: pp. 42-43) has written about the field-name The Jib in Linlithgow, which Macdonald’s (1941, p. 153) The Place-Names of West Lothian interpreted as a shape-name.[1] Hough notes that shape-names don’t often refer to sailing and that The Jib could instead be grouped with place-names referring to sites of executions, drawing comparisons with English names such as Gib Close and Gibbet Cospe inter alia. This should be borne in mind here as a possibility.
Against this interpretation are the fact that both Jib and The Jib refer to triangular pieces of ground and that and that overwhelmingly Gallows- is used in Galloway (and elsewhere in Scotland) in place-names associated with hangings; I believe Gibbet Hill, Crossmichael KCB is the only gibbet place-name in Galloway. And as the Place-Names of the Galloway Glens notes, Scots gibbet can refer to devices for hanging pots and pans not just the gibbet: “there may have been some gibbet associated with this hill which was not actually a gallows.”[2]
So, while it’s possible that Jib might refer to a place of execution, I think it’s more likely that the name refers to its triangular shape and that this name adds weight to the argument that The Jib in Lithlithgow is a shape-name after all.

Reproduced with the permission of the National Library of Scotland
Punch Bowl, Minnigaff KCB NX 418 646
“A large natural hollow in the centre of a field of arable land the appearance of the spot seems to have suggested the name.” OS1/20/97/19

Reproduced with the permission of the National Library of Scotland
Punch Bowl Wood, Portpatrick WIG NW 996 563
This wood is marked on the 1st ed. six-inch OS but is unnamed. It’s not as obviously shaped as like punch bowl as the example above.

Reproduced with the permission of the National Library of Scotland
Quarter Cake, Annan DMF NY 191 669
“A small patch of arable land at the south end of Ever Holm. It is bounded on the north and west by a row of forest trees, and on the south & east by a wall that forms part of the southern boundary of Ever Holm. It owes its name to its shape; being shaped like the quarter of a cake.” OS1/10/2/11

Reproduced with the permission of the National Library of Scotland
Roundhead Plantation, Holywood DMF NX 927 764
“A fir plantation of about 50 years growth. The property of Francis Maxwell” OS1/10/25/67

Reproduced with the permission of the National Library of Scotland
Sand Glass Plantation, Mochrum WIG NX 352 426
“A small plantation in Monreith Demesne, the woof of which consists of Oak, Ash & Beech.” OS1/35/75/37

Reproduced with the permission of the National Library of Scotland
Scythe Wood, Parton KCB NX 741 727
As above, this wood has the same shape on the OS 1st ed but isn’t named until the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Spectacle Wood, Glasserton WIG NX 373 425
This wood is marked on the 1st ed. six-inch OS but is unnamed.

Reproduced with the permission of the National Library of Scotland
Spectacle Loch, Penninghame WIG NX 349 688
The east and central of the three Lochs of Garwachie are named as Spectacle Loch on the current OS.

Reproduced with the permission of the National Library of Scotland
Square Plantation, Kells NX 672 714
“A small plantation consi[ting] of Ash oak and fir wo[od] on the farm of Nether [Airds] it is of a shape nearly [square] hence its name.” OS1/20/81/56

Reproduced with the permission of the National Library of Scotland
Square Wood, Ewes DMF NY 382 915
There is no wood here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Square Wood, St Mungo DMF NY 138 742
There is no wood here on the OS 1st ed. The link above is to the 2nd ed.

Reproduced with the permission of the National Library of Scotland
Square Wood, Minnigaff KCB NX 475 636
This wood has a similar shape on the OS 1st ed six-inch but is unnamed.

Reproduced with the permission of the National Library of Scotland
T. Wood, Tinwald DMF NY 047 827
T. Wood on the Os six-inch 2nd ed. looks nothing like the letter T. However, the 1st ed shows a thin plantation called Hunterhouse Plantation which is clearly T shaped.

Reproduced with the permission of the National Library of Scotland

Reproduced with the permission of the National Library of Scotland
Triangle Wood, Colvend & Southwick KCB NX 907 593
This wood is marked on the OS 1st ed six-inch but is unnamed.

Reproduced with the permission of the National Library of Scotland
Trump Wood, Crossmichael KCB NX 745 728
This wood is marked on the OS 1st ed six-inch but is unnamed.
TRUMP is Scots for ‘jaw harp’, which is a good match for this shape. Another possibility is ‘trumpet’.

Reproduced with the permission of the National Library of Scotland
References
[1] Hough, C. (2001) “Notes on Some Scottish Field Names”, in Names, 49.1, pp. 37-53 https://doi.org/10.1179/nam.2001.49.1.37 Available here.
[2] Kirkcudbrightshire place-name 1221 :’Gibbet Hill’. 2021. In Place-names of Kirkcudbrightshire. Glasgow: University of Glasgow. Retrieved 27 June 2021, from https://kcb-placenames.glasgow.ac.uk/place-names/?p=record&id=1221.
Update 27/06/21: I’ve added Float Cock Island, Kelton and a note about Jib, Kirkmaiden.
Update 16/05/22: I’ve added Gun Wood, Anwoth; Spectacle Wood, Glasserton; Spectacle Loch, Penninghame; and Half Moon, Glasserton.
Update 18/05/22: I’ve added Axe Wood, Closeburn; Scythe Wood, Parton; Ace of Clubs Plantation, Kirkcolm; Bessie’s Apron Plantation, Hoddom; Crows’ Nest Plantation, Kirkgunzeon; Roundhead Plantation, Holywood; Fiddle Plantation, Girthon, Hutton & Corrie; Square Plantation, Kells; Square Wood, Ewes, St Mungo, Minnigaff; Fiddle Wood, Lochmaben, Urr, Penninghame; Triangle Wood, Colvend & Southwick
Update 19/05/22: I’ve added Halfmoon Plantation, Old Luce, Sorbie; Horseshoe Plantation, Kirkconnel, Morton; T Wood; and alphabetised the list.
Update 22/05/22: I’ve added Trump Wood, Parton and Dragon’s Eye Wood DMF. I’ve also added a summary of the numbers to the introduction.