Backdrop is an improved site background customizer allowing for all manner of fancy things.
Backdrop is a site background customizer with power greater than the mere stock background selector included with WordPress. What can backdrop do that the default can't? I'm glad you asked...
Note: Starting with version 2.0 Backdrop will no longer work it's magic with older versions of Internet Explorer (before version 10). IF you want to support animations on older versions of IE then please use Backdrop 1.X.
Note: Your Backdrop settings will not be transfered from 1.X to 2.X, you will need to re-set your backdrop on update.