This one is the four-level poster.
This one is the three-level:
And this is the black & white/2-level:
The differences are that the three have different levels of “posterization” (reducing to few colours). On the bottom is one at 2 levels (black & white). The others are 3 and 4 levels respectively upwards from here; you can notice it most clearly under the glasses, where the more-level versions have a small gradient of greys to go from black to white. Personally, i think the 4-level one is the best, with that slightest softening of the harsh black/white lines.
Could do it in white on black, but I think then I’m going to want to add a faint outline to the black areas, to just give them a hint of definition.
Played these ones straight (pun not intentional), no antlers or octopodes, but can definitely look into that kind of alteration once I’m happy with the basic format. :)