Noses should also exhibit top, side and possibly bottom planes. The ball of the nose should overlap the nostrils and should not only be shaded on the lower half but should project a cast shadow as well.
And lastly, the mouth should be drawn with a subtle arc across the dental sphere. The upper lip is generally darker than the lower lip. In addition, the mouth will have more volume if the lower lip is rendered with tone and limited line rather than totally outlining the shape.