From a more esoteric standpoint...;) First, you need a good story.

Second, you need to make people care about your characters. Have them interact with each other. For example, you can have each character's eyes look at the eyes of the other characters. Think about how people interact. (no disrespect, but this may 'offend' a few people). Say a sword fight.
In reality, you want your feet placed right, you want to be watching the eyes of the opponent, or at least the sword, or raygun, or whatever. If someones' swinging a Mega-ginsu at your vitals, you're going to react to that.  You've already covered this, but this is more about how... So have the eyes looking at something or someone.

That being said, this is the closest I've ever gotten to pulling it off...;)

http://www.renderosity.com/mod/gallery/index.php?image_id=1693283

Third, the environment. Lighting and textures are 2 things I think really make better pictures. Some shadowing, using lighting to convey the tone of the picture (for example, the old 'light shining up from below to the head can convey a sense of menace" kind of thing.

And finally, I think consistency is also key. The character should look the same from panel to panel (subject to damage, character development, etc). Continuity helps to ground the story, so you can miss an issue and still have a feeling for what's happened.

That's all I can think of for now.

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)