THX1138, (great movie, BTW)
One can do a lot with the full version and with some
bit of practice one can create a pretty good head
character from a photo (use, fine tuning and higher
resolution, plus one can zoom in for more precise
placement).
Bear in mind that one can not create any full body nor torso characters with PP. They can be greatly modified by using a template and a decent paint program.
The small screen size has little to do with the final outcome of
your character as it's size can be enlarged / reduced at will, once in the confines of the Hal window, for instance.
I've seen hundreds of character heads and none look the same. Jackgephart (as well as several others) have created remarkable celebrity look-a-likes and custom creations.
Hey, you only get one ticket on this ride...ya might as well have some fun!