This actually isn’t just for Ganty. It just involves a little CSS. I needed it for a section in a Gantry template, but you can use this anywhere.
I got this set up from good old W3Schools so you know it is solid.
It is really just locking down the position of the background image and setting it to cover. I didn’t have to specify the height of the div in my case.
I hope this helps someone else out there…