The background. The environment feels almost like a diorama because it’s small and has no depth. Depending what you’re going for, this could be fine. If you just need something to display your vehicle on, this is perfectly serviceable. If it’s supposed to be an environment, well you need more environment.
The ground actually looks pretty good! It’s just a tad more lifeless than most deserts, and there’s no background. Using a brownish mist/atmosphere to hide the ground’s edge mostly makes the image look dirty and hazy and doesn’t really hide the lack of depth.
If you look at these desert photographs, you’ll notice that even relatively flat deserts have visible land forms off in the vast distance (as well as a bit more plant life). For a hazier scene, see this one. A lot of workflows use those as a separate mesh instead of stretching their foreground plane that far. You could also use an image of a mountain in the background.
Ohhh yeah, that’s it. How’d I forget about tumbleweeds?
I don’t know, but tumbleweeds would be a great addition.