Add background image to a region through the UI

So, it's relatively straightforward to add a background image to a region through the theme with custom css. 

I'm trying to find a way to do this through the User Interface, either through a contrib module or some other trick. 

We have the option to add a background image to a hero block. How about adding a background image to a region?

I'm open to any of the following types of answers:

1) A Drupal module that might be ported to accomplish this
2) Some pseudo code on how to write a module for this feature
3) Some creative use of core features that might make this possible. 

CSS injector doesn't count! (It's a reasonable option, but I thought of that already).