I have seen many flickr / pinterest posts about people using RIBBA frames from IKEA, so went to pick up a few a couple of months ago. I found something called the KASSEBY display case instead, and they are absolutely perfect for displaying minifigures.
You could probably build a background that is a lot less random and a bit more elegant than here, but the box itself is ace. Deep enough to display some builds, I reckon and "shelves" can be put in at the height you want. The box is six studs deep and 52 wide.