I've seen this done on a few sites, and was bored last night so I gave it a go in Photoshop CS. Turned out great. I used a woodgrain pattern for the background, looks like a bunch of pics sitting on a desk. I made up a polaroid frame, which I attached in case anyone else wanted it. After merging the car picture with the frame, I bevel & embossed it, drop shadow, and tweaked each of those a bit until they looked fairly realistic. Very simple process, all it takes is some time.