Picture 1. Eye lids are created by copying edges inwards.
Activate border sub-object mode and select all edges surrounding the eye hole and create new polygons by copying edges inwards according to picture 1.
Picture 2. The mouth is created by copying edges inwards.
Picture 3. Polygons inside the mouth.
Select 9 edges surrounding the hole in the mouth and create new polygons by copying edges inwards according to picture 2.
Activate polygon sub-object mode and use Editable Poly's "Hide Selected" and "Hide Unselected" buttons to hide all polygons except the ones surrounding the mouth. Create new polygons inside the mouth according to picture 3.
Picture 4. Complete 3D model of a human head.
Unhide all polygons and finalize the head. The head is now easier to finalize because all polygons have been created. The complete 3D model could look for example like in picture 4.
It should be fairly easy to modify this model for example to more realistic or more stylized direction. If you wanted you could use this 3D model as a base for many different 3D characters. Let your imagination fly!