The easiest way to make a assymetrical head without a seam , is first draw the head symmetrical, then copy both sides and flip them horizantal, so that the back would be at the front, & vice versa, since the front won't get a seam as long as you don't go to close to the edge, draw what you want, smudge it a little into each other(Both sides crossing over), then flip them back, then gratz, a seamless assymetrical head.