Nice picture. It looks very realistic. One problem with a 2D image is that you might get reflections back to the eye-tracker if the image is glossy and perpendicualar to the eye-tracker. You might try a matte image. The eye-tracker is trained to find eye features from a large set of eye tracking images. A 3D head with artifical eyes will be excellent, but you need to have eye-lashes, eye-brows, eye-lids etc to have stable tracking.
Cheers, Peter