From:
http://en.wikipedia.org/wiki/Polygonal_modeling
"A second common modeling method is sometimes referred to as inflation
modeling or extrusion modeling. In this method, the user creates a 2d
shape which traces the outline of an object from a photograph or a
drawing. The user then uses a second image of the subject from a
different angle and extrudes the 2d shape into 3d, again following the
shape’s outline. This method is especially common for creating faces
and heads. In general, the artist will model half of the head and then
duplicate the vertices, invert their location relative to some plane,
and connect the two pieces together. This ensures that the model will
be symmetrical."
I'm very excited about your work! I can't wait to see it evolve.