Woah, DecalGirl is pretty fast in releasing new skins.
By the way, if you people want to customize your own Wii U skin, you can wait until http://www.uniqueskins.com releases their Wii U skins. This site is pretty good when it comes to importing, resizing, rotating and arranging any picture, even in layers. The skins themselves are also pretty nice. They've released one for the Wii, 3DS and even 3DS XL, so I don't see why they wouldn't make one for the Wii U.
Yeah http://ww.skinit.com also has great customization to create your own but didn't release a Wii U version yet.