I was only able to use the three colors within the piece. Black, white and dark grey.
You used pure black and white and that can occasionaly cause some issues (since there's nothing darker than black or lighter than white to use).
I agree with Crafty that the eyes don't need dithering. If you introduced a couple grays into the mix to use for textures and AA, you could greatly enhance the look of the image.
This would look great with a lighter grey (was that not possible?) Anyway, it's still very nice as it is.
:=0 very cool