If you have some good backdrop images that are free-to-use, I can see about getting them into the next version.... I have wanted some new backdrops but haven't had the time to try to create or find any.
Most of them are more complicated than simple pics; they are a set of pics stitched together to support 360 degree (or close to it) view. The one in space is a simple picture.
Yes, it would be nice to allow the user to select their own pics as backgrounds. I'll enter that in as a feature request. There are a *lot* of improvements to Photo Studio that I would like to see; none are likely to be included in the forthcoming release, which is feature-frozen at this point.