This is so great. Another fun trick we used in the 90s was palette animation -- by swapping the palette you can create incredibly cool effects at a low runtime cost.
Changing the pallette mid-frame is fun, too. You have to pay a lot more attention to timing since you don't have a copper (like the Amiga) on the PC, but it's still feasible.
it used to be a hardware thing, so if your pixels were represented by a nibble, and the definition of the color for each of the 16 possible value is in table the hardware references, you just update that table (on a vsync, or even an hsync) and you could get cool animations effects (for the time)
random example from the Atari 800xl https://www.youtube.com/watch?v=uPjLZ4MVKCc (you can see how slow it is to draw a scene, but the animation effect due to pallete rotation is really fast).
http://www.effectgames.com/demos/canvascycle/