Checkout this before and after view of how one of my stock images was used on a book cover in Spain. A few years ago I photographed the pistol using some basic studio lighting as part of a series of photos that used a gun as a prop. From the beginning the series was targeted (pun intended!) for the book cover market. This one was licensed through Arcangel Images. You can see how the designer flipped it and used it as a mask in Photoshop to paint in another photo (not mine) into the final image. I like the technique and will try using it myself on future work.