Screenshots will only be 'pulled' if and when their wallpaper is not appropriately/sufficiently obscured which can create a copyright/distribution 'issue'.
Wincustomize.com is probably the ONLY site on the net that has this limitation/restriction with screenshot submissions.
The only OTHER time a screenie might be pulled is if it's simply porn or similar [...eg racially vilifying in content] or if a skinner or wall artist has had a specific reaison for a work NOT to be shown...eg...an inadvertent 'exposure' of a restricted artwork subject to commercial limitation.....[you show a friend a WIP for commercial/private release and he inadvertently makes it 'public' prematurely].
Otherwise, screenies are NOT restricted, though it's difficult to understand the motivation of the odd one or two to want to submit so many so often....