He's an generic NPC/Enemy, so he's faceless, but i don't know how to improve his first frame.

Eep, jpg! You should always save and post pixel art as png or gif. Jpg is lossy, and while it's fine for the messy blur of pixels and colors in photographic images, it does horrible things to your carefully placed pixels and thoughtfully hand-picked colors.

Also, many image hosts convert bmp to jpg without bothering to ask how you feel about it.

Couple things I'm thinking are off with it here. First, he seems off balance, like he's leaning too far back. Second, the hat is a little odd, why's it so pointy? Next, his waist seems to drop too far on our left, his right. This is probably what has me thinking he's off balance, too. Lastly, the shading on his legs and arms are coming from different directions. You need to pick a direction. Sorry if I seem to be too critical, I tend to sound that way. I like the color choices a lot, they're good. You could probably reduce it a bit by using the shoe colors for the gun.

Nice sprite, keep working.