I wasn't the one who suggested it, but flipping the image can be done a lot of ways. The quick and dirty way is to copy, rotate the copy and paste them back together in photoshop or some other processing program. You can then spend as much time as you want making the line between the images go away or not go away. Look for a image with the light from behind or in front of the subject. It gets a little weird if you have shadows going in two different directions. I have seen really cool things done with perspective and mirror images too.
I think this one would be fun and it would be great to get everybodies tips on how they did the flip