This isn't a hack, but I did something similar on my board too. I'm asking visitors to optionally build this into their signature files using UBB Code images.
I changed the wordlets and built a javascript pop-up help page which shows up as people register which explains how to incorporate the images into the sigs. I host the images, which for now on my board, are for my registered users families.
You can see it in action on this page.
http://www.twinstuff.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic&f=48&t=000024 I did it this way to keep it simple and also because my profiles are already becoming fairly crowded with avatars, flags and the other required details...
