About 13 years ago, I created some custom backdrops to go behind what were some of the original "Tin Plate Trackers" modules. Owned by a fellow modeler and friend, Dallas Dixon, we did a lot of repairs and improvements to the modules so they could be used for public display again. At the time I had access to a large format color printer. The images were cut and spray-mounted to hardboard backing that was clamped to the back of the module.
The concept was to depict Arizona from the deserts to the Chapparral and finally the tall pines of northern AZ. The images were pasted together using Photoshop to create the various transitions. The only downside was that being printed on bond paper, slight changes in humidity allowed some of the back drops to bubble, but overall, it was a great way to add depth to what was a 24" deep layout. We had enough backdrops to do about a 12'x40' railway as I recall.
Adding backdrops is a great way to enhance our little worlds and make them feel bigger.