Hey there! First of all, I think you already created yourself a good foundation for further rendering, well done! What I'd suggest at this stage is being more confident and bold with different values. Just by adding some new tones of black in the eyes or on the eyebrows do make a great difference here. Generally a good approach to kind of predict where which value should be, is to think about the area you are currently working on and then ask yourself where the light would have the hardest time to reach. At the nose, for example, the hardest part to reach for the light are almost always the nostrils. Therefore you could lower them in value even more. I hope this helps to some extent. Keep on going! | Artwod Feedback