User selected background-image from SF assets?

I'd like to have the ability for a stock image control added to a page to be able to make the selected image a background image instead.
ie: The client is requesting a unique browser-wide hero image for each page. They want a 2000px+ wide image that will be centered with the site, and be able to easily change it. If done using a normal image widget, the end result will get a scroll-bar as soon as browser is below 2000px.
Can this be done stock? Or very easily with a custom control?

Hey Nik,

You can build a simple custom control for this.
Add a literal to it, use Thunder to add a designer, make it a guid and Image Selector.

Then in your code behind, build out a style rule, which inserts the image as a background url.
You could hardcode the styling, do it by means of a css class or extend the control for various options but the proper css rule set would be: