I Forbid You
I formally forbid you from using one of the Twitter default backgrounds when you set up your profile. Unless you’re a solid green in support of Iran, you should absolutely have a custom background- it’s free advertising space on one of the most highly ranked sites in the world. I highly recommend hiring a graphic designer to create a custom image for your background with at least your website URL featured. This is great opportunity for branding as well as prime real estate to point viewers toward your other social networking efforts.
In the Meantime
If you’re not going to hire a graphic designer and your logo isn’t very sexy (sidenote: a tiny logo tiled across the page is ugly a sin), below are five sources for pimping out your Twitter wallpaper. On some of these sites, you have to dig to get to the good stuff, but it’s better than your solid color wasted opportunity!