I agree with Jezi and others. This is, in a lot of ways, a great piece. I really like the background and clothing details. As a martial artist, though, my first reaction is "what's happening in this fight?" This freeze frame does not feel like part of a fight, because fighters wouldn't be responding to each other in these ways, and I'm not quite sure what movement they're making. Is the man on the right thrusting or swinging his weapon? Either way, there needs to be more follow-through in his torso and arms (and support of the move in his hips and legs). Is the man on the left just pulling back to avoid a swinging blow? If it's a thrusting blow, his movement makes no sense, because he's about to throw himself off balance and topple over, and he's exposing his arm to the blade. If he's just pulling back, why is he holding his weapons as he is? What was he doing that led him to pull back with one arm exposed across his face and the other exposed out-stretched?
There's a lot I could say, but I think the main question here is "What's going on in this fight?" Where were they a few seconds ago and a few minutes ago, and how does this affect their movement (and expressions) now? Where will they be a moment from now? How do these moves follow-through? Understanding how they've been moving and will move will help you understand how to position their bodies right now. Don't be afraid to get up and make the movement yourself, and ask yourself what your muscles are doing, where your weight needs to lie, and how your body turns.
How long have they been fighting in this battle (level of adrenaline, fatigue, even cuts or abrasions, given that they're using blades and fighting in a stone environment), what kind of experience do they have, and what's their relationship to each other? Why are they fighting? Their motivation and what's at stake, as well as what kind of warrior (or non-warrior) they are has a profound effect on how they'd fight, whether they'd be getting sloppy, etc. Is one an aggressive fighter, and another sly? Zen? Zealous? Sadistic? Playful? Arrogant? Brutal? Patient? Desperate? Honor/code/ideals-bound? All of this affects how they move/fight, their expressions, etc.
Keep up the practice. You do excellent still work, and this is a good bit of progress.
The movement and detail here is great. It has a good dynamic edge. It might get more drama with some darker shadows on both the characters as well as the backgrounds, but that's your own choice of setting. This is really strong and eye-catching. Nice work.
To echo Fallimar there, sense of movement comes from the relative position of the head to the chest to the hips to the lower legs. In sketches, try stacking overlapping the head, chest and hips, then spreading the legs out wide -you'll get a sense of impending action. Spread them all out again and you'll get a sense of completed action.
The knife fighter is good; somewhat exagerated, but good. The mace fighter (which looks a lot like Oblivion's Elven mace... ) is an unfortunate example of feet of clay -great detail, great painting, weak linework. The shoulders and hips are working exactly opposite the action, so it steals all the motion. Either the torso should be moved over so that the right shoulder should be sitting almost where the elbow is now, or the hips should be over so that the butt is behind the shoulders and almost off the side of the picture.
For my own part, I've found that photoshop is an incredibly powerful tool for posing and aranging the innitial lineart, and makes setting the action and direction of a picture a thousand times easier -even when the finished product isn't in a digital medium.