1, 3 and 6 are really nice. I think the 3rd card is the best, really like the crispness the character has. I do think more could be done with the clouds in 1 and 3 though to make them pop more and would really complete the card. Is that Bilbo in 6 by the way?
2nd needs more facial detail since it's the central point of focus and I think the 4th could use more inking on the character as well; and not sure I like the facial shadow on the 5th card either.
All in all they are really good though. I'm still struggling with those damn Marvel stick figure drawings