Much thanks for the extensive feedback and example. It really means a lot. I'll keep it in mind

Sure! First of all, making faces look good at this scale is very difficult. Many people prefer to just leave faces blank, or do the eyes and dots and not even pixel the mouth or nose. There's only so much you can do when you have 5x4 pixels to work with. Everything will be dots or short lines. So if you want to work on faces, I recommend you go bigger.

The low resolution also makes it impossible to get the proportions right. This looks weird because you have the same distance between the jaw and the mouth (1 pixel), between the bottom lip and the bottom of the nose (1 pixel), between the bottom of the nose and the bottom of the eyes (1 pixel), and between the bottom of the eyes and the hairline (1 pixel). These proportions are wrong and you can't do anything about it at this resolution.

If you remove the mouth, then you can at least create an illusion that everything is in proportion because it's invisible. You could do something like this. 

Thanks. I'm still kinda unsatisfied with how the face turned out. You got any feedback?

Quite nice! Like the pose and subtle coloring. :)