Everyone has heard of photo montages, undoubtedly for it not to look like a montage you need a lot of skill and professionalism, but you can make a start with a program like Photo Crop Editor 1.05.
It lets you take elements from a photo and insert them into another background or with other elements or different objects, letting you create compositions or collages of different photos in only one scene.
The most interesting point for this program is that if it detects a big chromatic difference between the background and objects, it will attempt to match and automatically retouch that colour contrast.