Twitrounds is a large collection of free backgrounds. You can use their installer for automatic changes to your background or download the image and do it manually.
Each background shows the statistics of the number of views and ratings. When utilizing the automatic updating, you can choose whether or not to automatically follow Twitrounds as well as when it was added to the collection.
Lastly for the manual installers, they give you all the color settings you need with the download of the background itself. If these all remain free and the site ad driven, it will be a great resource. I didn’t see a count of the total number they have available, but it looked like a decent selection.
Update from the site founder!
Some other extra information in case you were interested:
- A little over 300 free backgrounds and we add between 5-10 backgrounds a day
- We are about to launch a Custom Twitter Background section for $79 per background
- Auto-Install tool that makes it super easy to install backgrounds
We do take requests for community backgrounds if people follow us and tweet @ us