Vignette can be faster if you convert the white to transparency in the image (therefore using .png and not .jpg)
A small menu icon update could be added to move the shadow in the direction the eyes are pointing (this gives the effect of a rotating character, and not just a 2d face looking)
If you look at a ball and don't change your position but the ball is rotating, it's shades wont change.
Also i tried a transparent .png - for me there's no noticeable difference in fps.
Vignette can be faster if you convert the white to transparency in the image (therefore using .png and not .jpg)
A small menu icon update could be added to move the shadow in the direction the eyes are pointing (this gives the effect of a rotating character, and not just a 2d face looking)