I just think it sucks that Artists are being ripped in the name of Fan Art and was hoping to have a civil discussion about it.
Sorry for the hijack but it did relate to the matter.
Doesn't 'quite' relate....
Unfortunately, the concept of 'Fan Art' as an 'out' for copyright legislation was a purely American thing. It certainly did not exist in Australian Law [for example, and thus likely not in British Law]....not until recent Free-Trade agreements between Big Bush and Banzai Bush that saw Australia adopting the same [along with draconian film industry workplace agreements, etc], so 'Fan Art' and 'Fair Use' are defensibly legitimate.
Either way, Wincustomize.com is US-based and thus follows US Copyright Legislation.
Where things go a bit gnarly is with interpretations of what constitutes 'fan art'.
Uploading another's wall as a wall is simple theft. Uploading another's wall as a Logon is less 'black and white' than that. There is argument for what is called 'value-add' - in the case of a Logon only bitmap100 is that 'other's wall' ...the rest may belong specifically to the uploader.
In the end it will often come down to the original owner of a wall/whatever indicating they object to the use of their work [fan art or otherwise] and request its removal.
Yes, admins/mods cannot be omnipOtent, or omnipresent, so more often than not a potential 'issue' will go unnoticed/unflagged until "someone complains"...