Some of my favorite sites with blog backgrounds. They have so many I can never decide. My favorite is http://thecutestblogontheblock.com/. Try it out. Some others are:
This has a lot of simpler blogs.
This has a huge variety with a lot of holiday designs.
Simple backgrounds with outside decorations or just a background pattern that covers the whole thing.
Here are just a few. I hope you like them. Anyways, enjoy!!