1.Sig's shouldn't be huge, I think around 500 pixels wide should be fine. If its do big we will ask you to reshrink it.
2.All avatars and sig's should not contain any adult imagery.
3.No youtube videos in your sig. Well you can link to them, but don't put a little video player in your sig. Unnecessary and slows down computers.
...ya..Thats all I can say for this...not even gonna put in a character code.