I've a few theories, but I only remember one...
Huh, my #1 theory
You have a picture frame, which has a resolution of 320x200 and
16bits of colors. You can put any picture into this frame. But there'll always be a limit. What's the limit? The limit is:
320 * 200 * (2^16)
Man, can you count that?
Or a smaller one, say 4x4 pixels with two colors
thus you can have 4*4*2 combinations of pictures, either a box,
a circle, a face or whatever. 4*4*2=32 combinations of pictures

So, my point is, if you have a rather fast video card and cpu, you can write a program looping to display all the combinations, not fooling you, your own face could be there!

Great, huh?