make a monster:

1. take a picture of yourself (works best if your head is at a slight angle),
2.
import the picture into some sort of imahge editing software (Photoshop,Paint, etc..)
3. copy half of the image, flip it along its horizontal axis, and line it up until it matches.

 
Below are galleries of submitted moster pictures:
 
gallery7
gallery6
gallery5
gallery4
gallery3
gallery2
gallery1