We all know about photoshopping and the way it has made photographic "evidence" the least rather than the most believable indicator of underlying reality.
For the next step down this road, consider this project from Kevin Karsch, a PhD student at the University of Illinois / Urbana-Champaign. Its official title is "Rendering Synthetic Objects into Legacy Photographs." Once you realize that "legacy photographs" means "real photographs of something that actually existed," and "synthetic objects" covers just about anything you can imagine, you have an idea of the potential. But check it out (and be sure to listen to the narration):