WALL OF TEXT APPROACHING.
First of all, I feel ya about the scanner. Art really loses something in the digitizing process, i've had that problem many times myself.
Now, I'm going to be pretty critical for a minute here, and I really hope you don't take it as a personal attack or too harshly, since i'm trying to be helpful, not mean.
I think the biggest issue is proportioning. You seem to draw heads, necks and bodies a bit out of whack from eachother. Also, when drawing two characters, especially with similar builds, try and make them as consistent as possible to each other, (shape wise) since that will give your drawing balance and overall a better look.
When doing faces, it helps to make them as symmetrical as possible since for the most part people's faces have a symmetry.
NOW I am no authority on art, nor am I a professional but I can give you a tip that helps me every single time:
Something you may want to try to get your people's faces, and bodies, for that matter to turn out better is this: try drawing guidelines (don't be afraid to erase later) and try to get everything laid out before you put in ANY of the details. This will help you achieve the natural human symmetry as well as allowing you to fix anything that's wrong before you go through a lot of work.
I made a simple little example of what i'm talking about.
Note that I have had, in the past (and continue to have) many/all of these issues I'm trying to help you with, so i know it's tricky.
ALL THAT SAID, I like you art and I think you have a lot of potential, and if you're serious about trying to be a better artist, I strongly encourage you to keep up the good work.