I own a small skin store so hopefully I can provide a bit of insight for what has helped for me. For shapes:
If you have ONE shape for a specific skin, it's optimal to have the vendor next to the Skin. That way, if people like the skin but do not feel like it fits them well they can visible see that they have the option of buying a shape that was designed to fit the skin best.
Also, ALWAYS have a DEMO. I cannot stress that enough. It's wonderful as a consumer to have that option so they don't feel like they are taking a risk by buying blind. It also saves you the owner the possib