There are 3 particular 'galleries' which are moderated on similar lines, mainly because all three are very similar in content....
Wallpapers
Logons
Bootskins.
The latter two are often exactly nothing more than a wallpaper sized/reduced to suit....often not a wall belonging to the uploader.
Logons are actually more than one wallpaper....there are other images to skin and other adjustments/choices to be made from the default XP look. When it's nothing more than a straight wall stuck in as image 100, and nothing else is addressed it's very likely to get the boot.
Bootskins are themselves a simple, single image, or two if you include the progress bar.
Ones without start looking all-wall-no-skin.
It is definitely NOT rocket science to reduce an image to 640x480 and 16 colours. If that's it, AND the image has suffered badly from colour reduction then again the boot-skin will likely be boot-ed.
It's painfully obvious that any and every image bigger than 640, and quite a lot smaller could be 'converted' to be a bootskin and the Gallery would be inundated with any number of 'XP this' and 'XP that', and heaven knows how many would actually have accompanying permissions from the wall/image artist to do so.
As I stated on mine [it was a test]...it took longer to reboot to look at my handywork than it took to create it and set it as 'active'. [I know they are 'quick and easy']....
So...
Let's try to make our submissions actually be deserving of being placed in these categories and not just because they have the appropriate file suffix...