Moose responded to you regarding avatars, but I've never seen a signature photo used at evc. I suppose you might try it by using an 'img=' command but sig photos might be something that the admins won't like.
An avatar can be added to your name on the left of your posts. Go to your profile by clicking on the first link at the top of the page. Scroll to the bottom and it will walk you through adding an avatar.
As far as adding a picture in your signature, I am positive that would be highly frowned upon, and suggest that you DO NOT DO THAT.