Since it is "Big Paws Only", it definitely makes sense to use paw avatars to rank members according to number of posts. That is what you are doing, correct?
Everything seems centered around "Paws", with Paw Print Profiles, etc. So, it could be like belts in Karate - arranged by color. To start out, a newbie may be identified by a white, red, or other color, and so on.
I hope that is helpful. Or they could start out with small paws and as they stick around and post they move up a size until they are biggest, and then they could begin colors according to posts. Such as after one has attained the largest paw print avatar possible, he/she then attains a color after so many posts.