Locate suitable pictures of drug paraphernalia. Even if you have some on hand, you can’t just slap any old image in and hope it’ll look right. You have to account for the appropriate lighting and positioning of the photo they’re being added to, so everything needs to match up. Any reflections on bottles should be hitting from the same angle, for example, and objects photographed at eye level will look obviously fake if dropped into an image that was snapped at more of an angle.