If you have a point and shoot digital camera, the macro function is your best bet for a close-up head shot. Take as many photos as your snake will tolerate, then go through them ruthlessly, choosing which ones appeal to you most. You'll soon build up more confidence and work out which distance and angles work best with your camera. I've just upgraded to a camera that lets me focus where I want and preview that length of focus before taking the shot, but while it works great on stationary objects, a lively snake is a different matter!