Ok i know there are some mythological creatures that are out there (mostly from Greek mythology) that KI haven't used yet. i would like to bring them to attention. Ideas of animation are very well come!
Hecatoncheires "hundred handed". They were gigantic and had fifty heads and one hundred arms each of great strength.
Giants Sorta like a cyclops, but like a normal human, just huge.
Ash Tree Nymphs I think these are just like the dryads. not positive though.
Typhoeus a fire breathing dragon with a hundred heads that never rested (sounds like a fire spell :P)
Cerberus The commonly known 3-headed dog, "brother" of orthrus.
Sirens half-woman, half-birdlike creatures who sang such sweet songs that listeners forgot everything and died of hunger
Argus Panoptes The all seeing. A man with many eyes.
Chimaera the Chimaera had three heads - lion, goat, and snake .Its body was also mixed having the front part of a lion, middle of a goat, and snake for a tail. It breathed fire.
Echidna A female monster consisting of half nymph, half speckled snake. It lived in a cave coming out to snatch up and eat those passing. The critter was ageless but, not immortal.
Pegasus (very common and, apparently, child of medusa and poseidon ) Pegasus was a winged horse and good flyer.