Twitter allows you to customize your background image and if you have good skills in designing and Photoshop, you can create good looking backgrounds. TwitBacks is a service which allows you to create your own custom backgrounds for Twitter. You can add your information to the Twitter background using TwitBacks, currently you can enter your name, email, short info about yourself, your website/blog details, your logo and personal photo, social networking sites etc.
There are currently 13 themes to chose from and the site mentions that there could be more themes coming in future.
Img Credit: TwitBacks
There will be a credit text at the bottom of the background and if you want it removed then this service is available for $9.99. The creator of this website also accepts custom backgrounds on payment.
Once you have created your profile, the download link is emailed to you. TwitBacks is a great service to quickly create a background for Twitter and worth a try.