i don't like being the guy but someone has to tell you the hair is awful
the lines are too big, and you can see the back of his head pretty clearly. don't know what you're doing with the eyes but they're plain boring and don't look good.
the overall expression looks like it was made in 2 seconds, something you'd doodle in class or something.
the color of the lineart is always black, it could be similar to the color of what it's supposed to be, such as the hair NOT being solid void/black and more similar to the hair color
only thing mapped well is the eyes, but the head just doesn't look good in my opinion. i'd look into how other people color in general. might help.
good luck.