I understand from what I've been reading is that the devs plan on adding more creature blocks eventually. That's good because I can't build all the creatures I want to build yet. So here are my suggestions (feel free to add your own.)

Fox
Deer
Dolphin
Butterfly
Moth
Horse
Cheetah
Tiger
Jaguar
Rabbit
peacock
Swan
Bee
Scorpion
Alien (grey type of aliens and I know they're not animals but neither are robots or plants.)
Crocodile
Wolf
Squid
Eagle/Falcon/Hawk
Mantis
Skeletal parts
Ghostly parts
Phoenix