Hot Bliggity Blog...If you use Blogger, you can pick one of several templates for free (actually, they ask for $1 donation, pretty painless), you can change them so easily by being in the Minima template mode and simply going to your Layout page and entering the code in your HTML/Java Script Gadget. That's it.
There are a ton of really cute backgrounds nestled between a lot of brown backgrounds, because apparently somewhere in the world, somebody likes brown. They even have Holiday templates if you are so inclined. Now, if you make the decision to upload a new background to your blog, I wouldn't go crazy alternating them if I were you. Blog backgrounds are like hairstyles, no matter how cute it is, if you change it too often, people will think you're unstable. But, there's always room for the occasional improvement!
Here are a few of my faves: