AbigailII: Actually, during a game, images can represent most of the abndwidth... and I know they should be cached but the fact is, many times they aren't (for instance, I have my browser set to display only cached images for BK, but sooner or later they go out of cache, either because I browse other pages or simply because some of them are very infrequent, like some positions in Backgammon or Chinese Chess, for instance). And some people simply disable cache altogether (I could really never understand why, maybe as a desperate measure to save disk space?)
So, a mirror image server might be easier to accomplish and definitely easier to manage... as it is, images are already served from a different server...

Anyway, Fencer will know if the images represent a reasonable percentage of the bandwidth to figure out if this could be worth exploring or not...