Trying to keep it simple, here are the possible faces I have so far:
Generally I like them. I think the mouth works in some of them and I think I am drawn more to the eyes in 17-19, which is why I thought I'd try adding some features. I think I like the faces most where the mouth is small and low on the face, giving him the traditional 'long face' of someone upset.
It's going to be difficult to choose though so any feedback is much appreciated! :D