Here's a little dive into how I created my concept Painting for My Area 51 Race Level.
I started by loading my car model, and a quickly made spaceship model into UDK. I built the ramp, the two plateaus, and the ramp supports out of BSP, and played around until I had a compelling composition.
Then I painted over it in photoshop. I changed the position of the car and the left Plateau to help out compositionally. I spent about 2 hrs making the BSP map (with a pre-made car mesh I made in Maya) and I spent about 10 hrs painting it in photoshop CS5.