In the skin preview images, the armor layer on the torso seems to render on top of the head layer, resulting in pixels from the upper part of the torso armor overlapping the head. For example, in this skin, the collar of her shirt covers the lower part of her face. In the 3D view, however, it is correct. I believe the proper way of making preview images should render the head in front, since that is the way it appears in-game. This is a really minor visual bug, but it makes any skins with pixels in the upper torso armor layer look weird in preview.