Anatomically, your figures are very short. Their torsos are only two heads high. Their legs are too short for their torsos.
Body proportions:
http://www.polykarbon.com/tutorials/body/sketch1.htm
I'm not sure whether you start from the head and work down or if you started from the feet and worked up. It looks like you stopped the character on the margin of the paper so they ended up short. While it's good that you're consistent about it, if you handle proportions correctly, you won't need to worry about that so much.
The pose:
Arms at their sides. Feet facing the same direction. Your characters are VERY stiff as if they're tensed and standing at attention. Next time you're in a crowded area, look around and study how people stand. How do they distribute their weight? What do they do with their arms? Notice that when they stand, their feet rarely, if ever, point in the same direction. Generally the feet are slightly less than 90 degrees apart.
A better way to draw the feet (only slighly better) would be to draw one from the side as you have it and the other pointing toward the viewer. This will give the characters a bit more depth.
Costumes:
Go you. You've obviously studied uniforms. Keep it up.
Wrinkles in clothes:
You have a few suggestions of wrinkles but nothing spectacular or for that matter, accurate. Wrinkles in cloth follow the shape of what's under the cloth. I would suggest studying the figure a lot more. If you haven't taken a figure drawing class, do so. Find books on anatomy and figure drawing. They will help. Draw real people whenever you can. Pay attention not just to their faces but to how they stand, sit, recline, etc. Pay particular attention to how the cloth stetches over their bodies.
Folds tutorial:
http://artcorner.org/tutorials/lessons/folds/laine/