The pic I used as a reference is a self portrait which I printed out, drew outlines in pencil on the pic, turned it upside down on the eraser and drew all over the back with the pencil so the lines transfered onto the eraser. Very faintly, but still. This is the third stamp I've carved; scroll down to see the others.
the first stamp I made (the second is the tiny envelope in the picture above):
the pic I based the stamp on:
Bird stamp which I've also carved, same size as portrait stamp: