If you're looking for beautiful, completely original art for your Zune, you should definitely stop by
Zunecards. I hadn't heard of this site before today, but it's really slick - their collection of backgrounds is small, but all very high quality. My only complaint is that it took a lot of clicking to download and unzip each of the 16 different backgrounds - I always wish sites like this would offer a single ZIP file with all their downloads, or at least one ZIP file per collection. Regardless, Zunecards is a site you definitely should check out!