From what I've heard/seen, they're having a hard enough time getting the dress-up for the human avatars to work, probably best to let them get that sorted before getting all ambitious with dressable creatus, even just rock ones.
Maybe as a new item collection, though. I also think "dyed" rocks should have some paint splatters on the "ground" around them.
Joppa seems to be the most popular so far. I should sketch up a baby and mutant at some point.