I'm not sure what the right way is to describe this but here are some examples. The examples are much more advanced than I need because I only need to have 1 picture.

I need something created where people can upload their picture and their face will be morphed, inserted or superimposed to the background image that I have. Example: someone uploads a picture of a baby crying (or any picture they choose) and the returned image would be the face of the baby crying inserted into a picture of a pirate or something.

http://www.famousdefaces.com/
http://www.morphthing.com/

I dont need any webpage formatting or style to it. Its just a plain generator that manipulates the image