I am slowly building a collection of "things" to put in backgrounds. Mostly I have extra people but I am starting to collect other furniture, as part of my own idea on doing positions. I just haven't had much luck getting the figures where I want them with the movement I wanted and determined that what I want probably cannot be done.
Your ultimate solution would be nice, but I think the only way to manage it would be through mods. And you'd need a diff mod for each location and size combo. Easier to make a position, load your plain background, swap to an image editor and pop in your object, save, and go from there.
I may need to figure out which image host to use, make an account and a gallery so people can pick and choose.