I love the scene you set up so far, really amazing work! You did a great job on making the ground look harsh and dry. Same with the rust on the barrels, and the worn out look on the market. I did a google search on cars with rust, and they usually don’t give out much reflections, and I can see some reflections coming off the car.
This is an image I found off of flickr. I know it’s probably not the same type of car as the one in your scene, but it’s close. So as you can see, looking at this car, as the sun shines off of it, you begin to see more of the rusted metal. I don’t know what node group you have set up in your scene, but probably consider lowering the glossy amount, and maybe adding a bump node to the texture of the car.
For the hills in the background, maybe add a depth of the field so that they aren’t as sharp or visible to the viewer.
This is optional, but maybe add some buzzards in the sky? Just to give it more of that abandoned desert look.
I hope my thoughts are adequate and not harsh. They’re just opinions, so it’s totally up to you.