Try this out, spot the difference game, very much like the photo hunt game in the arcade. This one, however, have a lot of other add ons, such as moving image, mirror image, and inverted image (omg this one sucks).
Each level have a few puzzles to solve and a new level will be unlocked if you clear all the puzzles in the current level. I am now at Teal level, where they first introduced the inverted image mode. I was so lousy at this mode that the above puzzle took me damn long and I had to cheat in order to find the last one.. well, i copied the image into paint and invert the image back again to find the last one...lol!
Ohh and there's the option of using "magic spot" to auto-spot the difference for you, but that one is limited as you only get one "magic spot" when you unlock a level.
Check it out here: Spot the difference!