We are creating an 8x8 matrix of RGB LED buttons. SparkFun sells a 4x4 button pad and circuit board for this. We're going to connect four of those together to make an 8x8 grid. When you press a button, it will cycle through 8 colors: red, yellow, green, cyan, blue, purple, black and white.
It would be cool if you could save these images that you make, and then show them as a slideshow, although that will be a secondary goal that we'll shoot for only after we get the LEDs and buttons working in the first place. The Arduino has 512 bytes of EEPROM memory (which will not be lost when you turn off the board.) You can read and write to this with the EEPROM functions. This would allow us to store 512/64 = 8 images.
I am unsure at this point whether we can run the 8x8 leds with one LED driver per color, or if we'll need one LED driver per 4x4 board. I think it depends on how the boards are wired. Since the drivers are not as cheap as I thought, it is kind of important that we figure this out soon. Or we could just order 16 of them and plan on adding them to the pool of available electronics, since they'll be useful for something else some day anyway.