Wall of Mugs
From the great (and sadly defunct) Readymade.com. I wish I had enough wall space (and spoons) to do this. (I have a habit of hoarding strange and interesting cups and mugs; my girlfriend hates it, but I could totally fill a smaller version of this.) Might also be good for a quirky coffee shop–when I lived in Pensacola there was a place that had shelves upcycled out of old bikes, and fixtures that looked like they’d been salvaged out of a dozen different abandoned restaurants.
Personally I’d use something else for the back–probably a hideous painting in a gaudy frame, like they have in thrift stores all the time. As long as you can clean it, maybe some of those antique-looking boards recycling blogs seem to love so much, or even an old table-top.