Cutsie rust monster from here [link]
I have coloured and added the corresponding letter.

First attempt at adding shading on MSpaint.

Let me know what you think.

Will have to make new list of pictures though.

List so far

A- Ankheg
B- Beholder (DONE) [link] (COLOUR) [link]
C- Cloaker
D- Displacer Beast (DONE) [link] (COLOUR) [link]
E- Ettercap (DONE) [link] (COLOUR)[link]
F- Fire Giant
G- Gargoyle (DONE) [link]
H- Hook Horror??
I- Illithid (DONE) [link] (COLOUR)[link]
J- Jackalwere (DONE) [link]
K- Kobold
L- Lizard Folk
M- Manticore
N- Nalfeshnee
O- Owlbear (DONE) [link] (COLOUR) [link]
P- Purple Worm
Q- Quasit
R- Rust Monster (DONE) [link] (COLOUR)[link]
S- Sahuagin
T- Troll DONE) [link] (COLOURED) [link]
U- Umber Hulk (DONE) [link] (COLOUR)[link]
V- Vrock (DONE) [link] (COLOURED) [link]
W- Wyvern
X- Xorn (DONE) [link] (COLOUR) [link]
Y- Yeti
Z- Zombie

If anyone has a request for one they would like to see, or a different suggestion, please feel free to let me know.