Custom Background Extended is the new WordPress plugin by Justin Tadlock. The plugin simply allows you to use a custom background color or per post basis in WordPress. It extends WordPress default background feature and allows you to overwrite the values for single posts using its simple meta box (on single post edit screen) that allows you to give a custom background.
Screenshot showing various background views for a single WP post:
Installation & Usage:
Install and activate Custom Background Extended plugin. Upon activation the plugin adds a metabox in add new/edit post screens.
Using this new meta box you can easily add a custom color and/or use image with additional settings on how you want your image to appear.
Screenshot showing custom background selection metabox on edit post screen: