I haven't forgotten you. I just needed to study the problem for awhile. Here's one thing I've spotted and need to do more code checking and analysis before I can absolutely say it's the problem.
The background you are using extends beyond the area of the listing that eBay normally allows for change, i.e. it's showing at the very bottom below the Description section in the Other options and links (page bottom) . I'm thinking that wouldn't normally be allowed and the Revise editor is catching and dropping the code. That suggests the entire page is set with that background instead of just the Description section. It's possible the submission from Auctiva didn't catch the problem (if it is a problem) at the time the code was received at eBay.
That's my best guess at this point.