One of the unique features of the plugin is to override the background and overlay of individual pages and posts, as can be seen on the Simple Override page, or by a post’s Category or Tag, as seen in the Category Override Example.
Another unique feature, is that each Image Set – a collection of one or more images used for the background – can also include its own CSS styling as shown on the Complex Override page.
Have you noticed the [ + ] in the lower left corner? Hovering your mouse over it will give you a thumbnail with a little more information about the background. And if you click it, you will be taken to page with the background image as well as the opportunity to see what other images are in the Image Set.
Of course it is also possible to disable Background Manager entirely on certain pages, such as the Search Results.
You can read more about available features on the About page.