Yeah I think you've got too much grass and not enough of the cars. Try to make it a little more dynamic. Perhaps stand close to the back end of one and try and get the other two in your shot as well. Get your depth of field going a little. How can I put this? Don't go for the typical photo. Try to get as many different and interesting angles as possible because they usually come out better more often then not. It causes interest in the viewer.
I like three the best though. The way the cars are facing make it look pretty cool.