Besides playing around with wallpapers it is possible to digitally modify a car, resulting in a DigiMod. A very suitable program is for example Adobe Photoshop. Digimods are another interpretation of cars that currently exist. Modify, re-design or tune a car the way you like it and the sky is the limit. I ran into this concept at www.digimods.co.uk.
As you can see below, some cars are just tuned, while others had a total conversion. If you click the links, you will see the digmods on large size, with in one of the corners the original picture that was the starting point. They are not without mistakes, but you can achieve quite nice results. However, it is more complicated and time consuming than creating wallpapers, exactly the reason why this section is not much updated...
Please don't put the pictures on your own site or link directly to the wallpapers and digimods. Of course you can refer and link to my website.