Professor_Markus
One of the problems you have is that you don't have that grasp of shapes yet from the looks of it, as well as the contrast needed.
In concept art, contrast+shapes pretty much makes the pictures. Right now it's almost like you're drawing things and filling it in (the eyes, nose) instead of draw the shapes and then adding the details.
Here's a craptastic genderswap to kind of illustrate my point. There's certain shapes that happen when the eyes are in shadow, but the eyelid adn even some of the brow area will be in light.

I can definitely see what you mean. Seeing a bigger version of the image, i'm kind of like "wow, uh, that sucks a lot." Because seeing it up close like that, I realize that I really didn't do nearly enough with this. I really appretiate your crit, and the craptastic genderswap did illustrate your point.. very well. I'll do my best to work on what you've pointed out, for sure.
Yeah.. it's kind of a bad habit I developed when drawing in Sketcher. Your space there is kind of limited and you share the canvas with like, 10 other people, so if you draw too big you'll be beat up.. over the internet.