A series of faces I sketched out and then inked in my sketchbook, scanned into the computer, and then had some shades of grey put in. I started off with a solid grey tone, and then added the light and dark values where needed.
Quick tip when trying to draw something like this out:
Draw a whole bunch of circles, ovals or squares out quickly. Make them all different sizes and get a nice pattern or composition. These will be all the faces. THEN start drawing all the different faces however you want. Makes it MUCH more likely you will have a nice composition of faces than if you just drawing faces randomly.