All right. After much scrutiny, I think I've found an area where you could use some work, and that's body language. Your faces and rendering are so solid that I often don't notice they're sitting atop rather straight, static bodies.
Now I'm not saying you need to go razy with exaggeration and superdramatic Draw Comics the Marvel Way, but maybe just put a little more thought into the bodies. A little more twist here and bend there, maybe for example the dude with the goggles in your last post could be holding whatever he's holding with two fingers extended, implying perhaps the motion of a nervous (or thoughtful) stroking of his whatever that is (is it a pen? the rigidity and position of the arm make me think it should be a backpack strap).
Anyway, I just think some more watching out for that sort of opportunity will give your characters more personality (not that they're lacking personality at present).