ok, so this has been sort of unofficially enforced, but I think that it should be added to the rules:
some people have huge images for their signature, to the point where it's taking up most of the screen, and it's annoying. so i think there should be a limit, like no image above 450x400 or something. i dunno on the actual dimensions, but something along the lines of a generally accepted sig, like one of our fine GFx members would make.