Fun with LED dot matrix

I just picked up a bunch of surplus 8x8 LED matrix and I wanted to have
some fun. They have column anode and cathode row (fairly common design
for dot matrixes) and I wanted to put it together and mount it on my PC
with random light flashing like some of those old 70's sci-fi shows.
Make it look like my PC's doing some serious computing.

Obviously the question is how I could do a random generator? I could do
a digital via computer but I don't want to shoehorn a C64 inside the PC.
Is there a simply DIY project somewhere explaining on random binary
generator? I'll probably have the generator on each rows and use 4017's
on each columns (with transistor driver)

Or is there a better use for LED dot matrix?

 

I've made a few prototype displays in the past, where each led mapped
to nn kbytes of the computer's memory (would need to be nn megabytes now)
and that isn't difficult to do. You can either use software for part
of this or all hardware. With current bus speeds it would take a little
more hardware to do this. But when you do this you can actually see that
your PC is doing something. Lots better than random blinking.