I discovered that you can use a program such as Google Sketch up to render objects such as buildings and vehicles and then print it out and draw and paint over them, or...import these assets directly into another program and then work from there.
It's free and although it takes a lot of practice to the get the hang of it, there are tutorials that you can watch to guide you along. you can get it here:
http://sketchup.google.com/intl/en/index.html
To show this example, I did a 3-D example of lettering that I then brought into Painter and then added paints, etc. to after.
1. In Sketch up, use the 3-D text tool to render any object that you like. You can export objects as images to use in other programs.
2. Then bring the object into a drawing or painting program and then begin to add effects over the image. In this case I added flames and smoke.
3. There are obviously many other things that you can do between Sketch up and other programs and this is just the start. Keep practicing and you will find new ways that work for you in no time.