Me thinks there aren't any regulations about signatures, since ArmorGames doesn't incorporate a signature section in our profiles. In short, there are no signatures.
People have created their own, from time to time, but it's a struggle to copy and paste the same thing over and over again in each post.
For example: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Everybody Wants To Rule The World
It takes some amount of effort to copy and paste that each and every single post :P -- and of course people post their graphics, pictures, etc. but I'm not sure what their sizes were.