This is a WordPress plugin called Custom Backgrounds for WordPress. I t allows you to put your own backgrounds to your WordPress theme.
With WordPress 3.0 a new feature was introduced called custom backgrounds for WordPress themes. This feature gives you the ability to add custom backgrounds on your site, which will your site a unique touch.
However have you ever wanted to have different backgrounds on Pages, Posts, Categories, Search page, Home page and Front page?
If your answer is Yes, then this plugin is for you. This plugin lets you add custom backgrounds for Pages, Posts, Categories, Archives, Home-page, Front-page, 404-page, Search-page, Author-page, Custom Post type.