"He who marches out of step hears another drum." ~ Ken Kesey
Not exactly what you're looking for but S&S Activewear offers high res images of just about every style and color they offer. Once you develop a system to pull those images, and build a library in your template, you can create stellar mockups. I have a feeling every vendor offers high res sample images if their products, I just personally find the S&S site very easy to pull from.