I'd like to know how to create the amazing effect used in this signature made by sugarpoultry for gimpyfish:



I love the way the image is split into loads of squares with different brightnesses and contrasts, and I'd like to know how to achieve this effect. Normally I would have PMed sugar to ask her how she did it, but she's away at the moment (or so her sig says) and I need to know before tuesday because I'd love to use this effect for some of my Graphics work at school.

I have Photoshop CS2, and any help would be greatly appeciated =)