STANTLER - Well yeah, Reindeer. I was thinking more like Bambi.
Antelope/Gazelle
ARCEUS (?) - I don't know what Arceus is. I think it's a llama.
Giraffe
GIRAFARIG - Yeah, good call, forgot about that.
Mosquito
Snail
MAGCARGO - Oh yeah..... but we need a proper snail pokemon. One that's actually bug-type.
Sqirrell
PACHIRISU - Again, good call, I forgot.
Donkey
Robin
Goat
Possum
Toucan
Dolphin
Killer Whale
Earthworm
Ant
TRAPINCH - Huh? *looks on Bulbapedia* Well, it's a larval antlion apparently, but I was thinking of, you know, ants. Those little black crawly things.
Armadillo
SANDSHREW - More of a shrew than an armadillo, but I can see where you're coming from.
Hammerhead shark
Polar Bear
Arctic Wolf
Cockroach
Electric eel
Tree frog
POLITOED - He's a pong frog/toad, not a tree frog.
Howler monkey
Koala Bear
Orang-u-tan
Zebra
Giant Squid
Stegasaur
Triceratops
Sabre-toothed tiger
RAIKOU - *looks closely at sprite* Huh, I never noticed the resemblence before. But no, he's based on the Raiju.
Mythical creatures not done yet:
Basilisk
GIRATINA - A little I guess, But not completely
Mermaid
DEWGONG - No, he's based on a Dugong
Centaur
Sphinx
Cerberus
Will-o-wisp
SPIRITOMB - No, the will-o-wisp is the creature with a lantern that leads people to their deaths in marshes. Spiritomb has nothing to do with it.
Egyptian Mummy (OK, not strictly mythical, but you know what I mean)
Vampire
GOLBAT - Vampire bat yes, Vampire no.
Griffin
Four Horsemen
Grim Reaper
DUSKNOIR - Hmm, to an extent, but I was thinking more a legendary pokemon strongly linked to the idea of Death, Dusknoir just has a vague association.