Trompe l'oeil trucks. From a truck-painting contest (in Germany?). Or maybe a truck-photoshopping contest, it's hard to tell from the pictures. Painting would be more impressive than photoshopping but either way, they look good.
... and all from the same single truck picture. It would be quite hard to get all the trucks in exactly the same position with the same tree in the background if they were real. Pretty cool though.
Snopes has the full story.
Thanks! So it is both photoshopped and a real truck painting contest...