Each website no the Internet has to wrestle with the issue of copyright. This is our policy.

Fair Use
Skins, themes, icons may use content created by others for the purposes of making what is popularly considered "fan art". So if you want to make a Star Wars based wallpaper or Superman skin you may do so.  We reserve the right to remove it in the event that the owner of the trademarked or copyrighted material objects (for instance, Marvel objecting to non-licensed use of Marvel characters) but in general we will accept skins, themes, icons, and wallpapers that are fan art as long as the user uploading them created it. Taking someone else's Batman wallpaper and uploading it is not going to be accepted. Creating your own Batman wallapper would be accepted.

Ports
Porting skins and themes created by others for a different platform or program is acceptable. Ports are often a great way for new skinners to learn how to skin.  My first skins were ports.  However, you must get permission to port the skin/theme from the original author in order to distribute it.  Porting of operating systems is generally accepted and would fall under the "fan art" rules. 

As a general philosophy, skins and themes that highlight and promote favorably an existing thing that is already known to people is acceptable. That is why we accept fan art but why it's not okay to take an individual's skins and port them without permission.