So the avatars and signatures are not very difficult or have many rules.
For the avatars all it has to be is appropriate so that means no nudity. The avatars can be of whatever you want, be it an icon or your pic but of course as I said before no nudity.
Signatures are yours to make. It can be what ever you want as long as its not too explicit (no nudity). It can be a picture (banner) or just written words. If you chose to put a picture in try not to make it too big.
Thanks.