I think dragons in signatures, while annoying, are perfectly fine. The problem began when posting dragons became a form of trolling. I never had a problem with Fingerz posting her dragons, because she never did it maliciously (except maybe to Patch, but he deserved it).

IMO, there should be a rule restricting them to people’s signatures. This way, they stay out of non-RP forums, cannot be used as spam in and of themselves, and would generally be less havoc-prone.