The last three images look really good there. You've cleaned up the John Wayne one very nicely, which would have been my critique on it. The shading kind of looks like it's not in the right places but if you have a reference I would want to see it. If you don't, I'd just comment that there's something strange about that mass of black on his face that looks like a rectangle. The wolf-ish dog is a very good start and my only problem with the snake picture is the man's head because looks like he's missing an ear and it looks as though his hair doesn't continue down the back of his head.
You have a serious talent for and knowledge of drawing hands. It's really nice. Good job on those.
"Yes, Ms. Flameel?"
"Multiply 47 times 83."
"Multiplication, it's math education! Isn't this swell? Oh, let's give multiplication a standing ovation...
so buy a calculator, study this stuff later!"
-Animaniacs (only a few good quotes from that song. Search "The Multiplication Song - Animaniacs" on YouTube
for this video and any other Animaniacs classic!)