Windows Media Player 12 has some inbuilt Library Background skins which some of you have already discovered and tried it changing from registry editor but for those who didn’t, here is Windows Media Player Library Background Skin Changer.
WMP 12 Library Skin Changer function is to change the background display on the Windows Media Player 12 library. These skins are already in your Windows installation but unseen and this tools lets you choose from those 6 skins (apart from default) and apply them in one click.That’s all, WMP 12 Library Skin Changer is a freeware portable tool compatible only with Windows 7.
Download: http://sourceforge.net/projects/wmp12lbsc/