Actually your face is well done, but where you could improve upon is maybe clear from the photo that Einion posted :
Look at the area's that we mostly call "highlight" area's, then you see a "warm" tone of colour (more "reddish" or "orange-ish")
Look at the area's that we mostly call "shadow" area's, then you see a "cold" tone of colour ...
From your pictures I guess you only just used dark or reddish browns for shading ...
Now if you'd paint in oils, I'd say add some - just he tiniest of tiny little bit - Turqoise to your shadow colours to cool them down, or to "gray" them down if you wish ... Use Turqoise for Caucasian types, and Ultramarine or Violet for fe. Injuns or Mediterranean types ... I'm sure these colours do exist in the vallejo acryls range too.
Result will be that the rest of the face will seem to have a more pleasing, warm tone. Also, you won't need such a dramatic bold contrast between shadows and highlights as you have done now.
I know it won't maybe work out right the first time you try this, but do give it a try ...
Hope this helps