It is Minecraft fanart in a way, because it's a Minecraft model. I'd feel wrong putting this in some random Art & Creativity forum because this is far more relevant. But hey, mods will move it if they feel it's necessary.
This is Fan Art, Nintorii. I think it's actually pretty cool. I'd like to see description on how the mob looks/works though. Be it passive and green, or purple and hostile to all. That'd be chill.
Well, the Forest Ostard is a passive ridable animal that is both bird-like and lizard-like. Its colors range from light blue to dark blue, light red to dark red, gold to dark brown, or light green to dark green. Its favorite food is fruit and they made semi-adorable sounds that resembles a large chirping type of noise. You can read more about them here (Note that I always use the 2D sprites from UO and not their horrible 3D.):
EDIT: I posted this in fan art, because it's not a mod and I couldn't think of any other appropriate forum. xD
Here I compare it to the sprite from UO:
And this is a closeup:
http://uo.stratics.com/database/view.php?db_content=hunters&id=173
Here's the colors: