Ahhh…then it’s probably not divs that you want but random background images.
I think you would have to have a whole bunch of images already set up and then use JS to tile them randomly in the background using a loop of some kind.
Or perhaps a multiple SVG solution utilised in the same fashion.
Sorry, I have very little (read..zero) ability in JS.
My only concern is that you would have to be very careful as it’s quite possible that this effect would make your actual content unreadable…at least in part.
Oh, one last thing…you might want to think about making them 96×96…makes the division easier.