Steps to Add a Style and Make the Facebook Background Change
1. Open the facebook.com home page in a separate tab.
2. Create a new tab and visit the companion website of Stylish at http://userstyles.org/styles/browse/facebook.com
3. Choose a style from one of thousands and click its name. The page with details of the style like its creator name, website and others appears.
For this tutorial, I chose a style titled Green color 2010.
TIP: Use the search box and search for a style, for example, by popularity (this is the default), style name and the date of creation.
4. Click the Install with Stylish button on the top-right. The “Install user style" dialog appears.
TIP: Click Preview to check whether the Facebook background change matches your needs.
5. Click Install. The style name appears as an entry in the Firefox Add-ons dialog. Now, view your Facebook page. Presto, your Facebook background change effort is successful!