I agree with a lot of what you said. 2nd photo is nice. 4th pix, it is not the contrast. It can't be helped as the car is in the shade, and the back ground is not. Too many f stops difference, no way a currently available digital camera can cover that much dynamic range. Back ground is too hot. But you did bring up a good point. Try to see what is in your back ground, and try to find lines that makes your subject look better. I'm guilty of the latter myself.First pic still looks out of focus and no real focal point.
Second pic would be nice if the dodge wasn't in the background. Because my eye can't but help to be drawn to the truck. Though that brings up the issue of what's behind the truck if it wasn't there?
Third pic is My favorite. Though it would look a little better if it was at a slightly different angle. A little higher and to the left. it would show the car better as well as cut that house out. Might even show more of the tree instead of just the top.
Fourth pic Try to focus only on the rim. The contrast is off in the background. Same angle but just the rim would work out.
Nice work though.
Which camera and lens are you using?