What about an approx. 45° side front and back view? Most hairs are more or less "symmetric", so I think it would be better to have a half-front and half-back view, so you do not need an additional third picture of each type.
What I think would also be very helpful is introducing a nomenclature for each type of hair (or just simple giving numbers or letters to them) which could be combined with color to reference a specific piece uniquely. If additionally this master plan of hair is "centrally" available somewhere in the Web there could be made references (in similiar way like currently into PlaymoDB or Collectobil) quite easily when somebody wants to describe a specific figure. (This is not only a suggestion for the hairs but also for beards, faces, etc.) BTW, if sparte part numbers are available for hairs (cf. socrates' list), these should also be listed below/beside the picture.