I second Neko; lately I've been browsing the forums several times every day for art-related threads. :3
We do discuss users' Creatu ideas from time to time and they've probably been used as inspiration before, but I think, in general, the pet artists find it less complicated to just design their own creatures from scratch. xD Not to say it's an impossible thing, though.
I like your design; we could use a few more aquatic pets. ^_^