There are a lot of websites that offer free Twitter backgrounds but Themeleon is a tool that clearly stands apart. Themeleon is a nice little tool by the COLOURLovers community that you can use to generate your own Twitter background within seconds.
Start with selecting a template; you can either browse through various template categories such as ornate, mosaic, simple shapes, nature, retro, stripes or check out the top templates. Once you have selected a template, click on the color thumbnail to open the color chart. Now you can choose any color in the world to customize the template.
For the color of your text, links, background and sidebar, you can either create a color palette or choose from over 1 Million available color palettes. If you like the colors of the template pattern more than the colors in your palette or vice versa, you can sync them with a single click. You can also create a background by uploading a photo and customizing it to your taste.
The most amazing feature of Themeleon is the ability to preview the changes as you make them right in your Twitter profile. Themeleon will ask you to login using your Twitter credentials so you can implement your customized Twitter theme with a single click. No need to download or upload anything.
The developers creating Themeleon thought of everything. It is quick, has a lot of features and gives you infinite possibilities for your Twitter background/theme. I have not seen a better tool around.