I have a lot of fun altering photographs. With car photos this often means replacing the background behind the vehicles or making collages of the cars.
The extent of the alterations and what I can create or change is usually only limited to my imagination and the amount of time I want to spend working on it.
These are some examples of alterations that I have done:

This image is created from three different photographs altogether. The car, the building behind it and the pavement that it is sitting on are all separate photos. The background was put together and turned to sepia tone then the car was laid over and the shadow added to anchor the car to the background.

In This Photo I removed the truck from its original background and created the new background behind it. The color of the background is taken from the truck to help tie them together.

Here is another instance where I took the car off of the original background and created a new background using colors taken from the car.