How about midi control? You could assign midi notes from a couple of channels to control the 256 pixels (extra credit: use midi control to actually set the color; maybe use velocity as a 6-bit rgb for coarse control). You’d need a midi processor of course, but people have already done that in arduino, and then you could hook up any kind of control matrix you want.
I’d love to do this but have never done anything with arduino. I’ve made midi-controlled animations with a Novation Launchpad and would love to do it with GameFrame!