No difference for all ranks, I've been wearing my current signature since newbie iirc. There are no chars count limits, use of tables etc., this forum allows you to use an images in your signature space with req. size of 400x60 pxs. So it would just need a lot less chars count.
Edit: just did signature code experiment, I can only use one image in my signature space. don't know about other ranks.
It would be great if we were allowed to have multiple images