There are programs that do that. You open a picture, and the program remakes it as a mosaic of smaller pictures (you can provide the smaller pictures too). This was done with an array of 32 by 31 pictures. All the guy had to do was rename the pictures so that when you zoom out enough to see 32 columns of photos, you get a girl's face. And I think the program also does that automatically.
Yeah yeah, I'm belittling his achievements. Bad me.