Im surprised that some of those studies are from Bridgman's, they are so angular I thought it was all Hogarth. The pointy-ness works in your cartoons but you might want to down play it a bit on the studies, just to be sure you're taking in the information accurately.
You also might want to consider shading more with the form on the studies, some of them are a little flattened out by the hatch marks.
I really enjoy your little cartoon heads, I have a particular preference to the bottom left on this page:

I'm sort of biased against the tiny, blank eyes. You will be fighting to get expressions out of them.