A Hot topic now discussed arround twitter is How to get a nice twitter background, well there are two options:  

1. Download and use any bg that are ready available to download from websites.
2. Create your own Twitter background.

If you have less experience with photoshop also i would still suggest you to go for the second option.

Some websites to download twitter backgrounds:

www.twittergallery.com
www.instantshift.com
www.twitpaper.com
www.twitbacks.com
www.mytwitterbackgrounds.com
www.tweakmytwitter.com

If you want to design your own twitter profile, here is a detailed tutorial how i made the below twitter profile!

What is Web 2.0: The term "Web 2.0" is commonly associated with web applications which facilitate interactive information sharing, interoperability, user-centered design[1.6] and collaboration on the World Wide Web. Examples of Web 2.0 include web-based communities, hosted services, web applications, social-networking sites, video-sharing sites, wikis, blogs, mashups and folksonomies. A Web 2.0 site allows its users to interact with other users or to change website content, in contrast to non-interactive websites where users are limited to the passive viewing of information that is provided to them.

Below are the set of Color codes that can be used for web 2.0 websites ( Originally compiled by Orangecopper.com)