Underpainting on some of the lit side of the head has given it more form, which makes the composition clearer. The inside of the ear will be much darker, as it is in shadow, and this should highlight that side of the face giving it more dimension.
Using tone, colour, intensity, contrast and perspective are elements that I try to combine with the aim of giving my work a dimensional quality. When the work is complete I will see if I have been successful.