New into pixel art (need some tips)

I came up with an idea for a game a few weeks back and wanted to do some artwork for it. However, I am by no means an artist, I am a programmer. So I am looking for some advice. I want to create a top-down 2D RTS game with heavy mod-support, probably as an open source project.

I want to go for a dark-medieval textured art style. Something like http://store.steampowered.com/app/239070/ (Except without characters that are so small).

Here is some of the art I have so far:

(Elven Archer)

(Flower Field)

(Decorative Rock)

I have three things I'd like some tips or help on:

* How do I go about the drawing the Elven Archer from a profile-perspective?
* How do I add a realistic looking face/expression to the archer?
* How do I make the images have a darker and more textured look?

TIA