Add Background dialog would make it easier for users to define how backgrounds will look without having to go through the Add Property dialog several times. One thing that I would enjoy is if there was a better way to add multiple properties which you usually add together to achieve something. For example, adding a background takes many properties, you have the image file, margins, stretching etc. There's even more if you want to specify DPI based images or gradient fill colors.
In the following video you'll see how this concept works. For each property that you edit in the dialog, it would automatically be added.
http://www.screencast.com/users/ThePandaX/folders/Jing/media/d0a79695-0d17-4cb2-b280-ffbe1492f4ef