Hi, welcome to the forums!
I like the vay you used varied lineweight in the chin and ears, and think that you could use a little bit of the same on the upper eyelids to give more depth to the stare...also, if you look at a picture of an eye, you will notice that the upper part of the iris shows darker because the eyelid and lashes cause a shadow... so I believe adding another, darker colour to that part of the eye will make the highlight pop out more.
On the hair, I think you are only missing highligts, the same way you have a highlight on the nose corner. Since you are going for a graphic novel style, why not look at the way some manga illustrators have solved the problem of hair highlights? probably you can find a treatment that points you to a solution that you like.
welcome again, and hope to see more of your work in the forums
snow rule # 2 when tobogganing, do not brake with your forehead...