My advice would be to set up a tripod and take a LOT of photos in a row. For example, with my stock canon point and shoot under the timer option there is a "custom" option that will shoot 10 shots after 10 seconds. Do this many times (or better yet, use an intervalometer on a very short interval) and try all sorts of expressions, postures (mainly staight back), angles, and whatever else you think of. Out of ALL of those you might get one good one.