I have think over and have this suggestion: to remove 800x600 resolution from wallpapers.
It is resolution that is lightly use (cca. 4% (and that is i think on old office/industry PC or so)). And when sombody use 800x600 he can use 1024x768 wallpaper, it is only few bites biger.
I think it will save some space and maybe little speed-up validating.

mmm... I see the point of saving some time validating... but I still think it is a good idea to have it, not so much for the few people that might use that resolution, but maybe they can be used for websites, since most layouts nowadays are 1000 pixels wide, they can easily accommodate 800x600 without modifications...

Space is not an issue at all, since we have unlimited, but saving a few seconds in validating is a very tempting idea