Got a day to kill with your X16? Run this BASIC program and generate this 256-color fractal plot. It's zoomed into a deep part of the Mandelbrot Set that is particularly pretty. This plot does up to 355 iterations and is within an area where all points require at least 100 iterations, so the whole 256-color palette is able to be represented, from white for 100 iterations to black for 355 iterations or more.
For fastest results, run in "warp" mode with your emulator:
x16emu -warp -bas x16-mandelbrot-vga-fancy.bas
At 8Mhz, this will take literally all day, but if you have a beefy enough host for your emulator, it can be cranked out in a couple hours.