I spent my lunch hour today experimenting with hacking JPEG files. I opened the original file with a text editor and went to town cutting, copying, pasting, and typing. Small changes to the text result in sometimes drastic glitches, so I saved and checked my progress after every change. Often I had to backtrack, having wiped away too much of the image for it to be recognizable. Worth playing around with, though entirely unpredictable.

original:

hacked: