This application allows you to mix two (or more) pictures into one montage. The pictures can be freely moved and resized, and you have complete freedom over which parts of the photos you want to keep. You can remove (or readd) areas with your fingers, like painting. With this technique you can create montages, replace backgrounds, replace faces, or combine pictures any possible way you can imagine. It is also possible to make semi-transparent pictures.
The application has no built-in limit on the possible size of the images, but keep in mind, that manipulating very big pictures requires a lot of memory and computing power, so the application might slow down, or run out of memory.
To test the features, you can get the lite version. It has all the functionality of the full version, but you can not save images bigger than 300*200 pixels.