http://www.beamng.com/threads/introduction-to-skin-system.16931/ http://wiki.beamng.com/Simple_skin_tutorial
You mean the UV to use as reference when making the skin? If you mean a sample skin that is already selectable ingame, like in the tutorial, there is none. The tutorial only takes the hatch as example. You use that as example to make your own for the van, which is not hard. The van also have some official skins already, explore the 'van.zip' and take them as example.
-- Post updated --- I don't understand how make liverys with the UV I make my livery van with what software?
With any image editor program you want. Can you please take 5 minutes and read the tutorial we spent time writing? It explains exactly your doubts. http://wiki.beamng.com/Simple_skin_tutorial Thank you.
As Nadeox1 said, read the tutorials, they explain what programs to use and everything. I learned how to make skins by reading the tutorials and trial and error, you can too, it just takes a little patience. Once you make one skin, it will be really easy.