Adding sig pic

How come I can't use the same pic in my sig that I did on the old board?
I can put it in when I reply,but when I try to add it to my sig it won't accept it.Do I need to shrink it or what.This is the pic I've always used.http://mediaservice.photoisland.com/auction/May/20045283518559997758875.jpg

You should be able to use that pic as your sig.