Hey I like your work, but I'm not sure if you're using references or not, are you?
I think the main thing that takes away from this art is that the poses feel a bit unnatural and stiff, like the characters don't have weight to them. It's hard to describe.
The proportions are not bad at all really, but the characters all seem a bit "floaty" which makes me think maybe they weren't done with a reference. I've had this problem with my own art, and I can only make guesses as to how to fix it since I'm still struggling with it myself.
Perhaps since this isn't super-realistic human art you could try using a "line of action" to determine something about the pose before you do your skeleton/wireframe. It's an old animation concept by Preston Blair that I've found helps give a bit more life to my drawings. I don't know if it truly fixes the weight issue, but it does seem to make my work my dynamic. It has helped me somewhat, so it might help you too.
I think this is a really good example of someone who's done some great human skeleton wireframes with action lines:
Lines of Action
And this is a screenshot from Preston Blair's book:
Preston Blair Lines of Action
And finally this is an image from my favorite comic book that I feel really has a lot of "weight" and emotion to it, and works really well to illustrate (hopefully) what I mean: