I am using one of these “complete” themes on my Firefox browser, and lately, as I was looking at the page with the usual image-based themes, and started previewing some, I could see that the complete theme I had would combine really well with a background.
To my great deception, though, it turned out that I can’t choose to use an image theme without bringing back the default interface.
Couldn’t you change that? Some of these “complete” themes you have on your website would come out great with some stuff in the background.
It was decided long ago not to support this because of the complexity it adds to the Add-ons Manager code, for what would probably be a rarely-used feature.