(ok-)
First of all I love the sketchy vibe you're going for!! It's very very nice, so keep that up. Anyways, I've noticed you've got a bit of same face syndrome-
That's something you can easily fix, so just work on your facial expressions
Anatomy and shading are pretty good overall so good job! Also your chins seem a little,,, pointy? I think it's just your style but sometimes they're a bit t o o pointy, so try softening them out just a tad.