you will have to do what you did with your gallery island with a custom island, but that is easy..
for each sponsor / image combo... put
<div class="sponsor_side_link">
<a href="http://sponsor_supplied_link.com">
<img src="http://www.prosanddrags.com/forums/gallery/28/thumbs/49.jpg />
</a>
</div>
change the sponsor link and the thumb from the gallery for each new sponsor you want.
you can style the sponsor_side_link class with css too...