-snip
I'm not artist pro, but those are something that I think would improve it immensely. It's kind of like how proper grammar, capitalization, punctuation, and spelling can make someone seem immensely more intelligent immune to Grammar national socialists.
-ahem-
Unfortunately, I am not a technical drawer, don't want to be professional, and I don't want to be an artist.
Indeed, the stuff you pointed are indeed, stuff which I used/didn't use too well on the drawing.
The grass, sunlight, etc. was done to create a specific "scenery", the grass, with the ground makes it a feel of a 4x4 car which is made for Off-Road, if it was a racing car, for instance, a road, or a racing lane, would've fit well.
"You can't have a tree without soil" ; the closest quote I can think of.
Either way, about the shading at the wheels, making it in segments sounded like a win of time.
About the pencil shading, it looks way better in real life, it's a scanner, not a human-eye-scanner. Obviously quality was reduced [or increased?], but lightning sure was, hiding some aspects. Or revealing.
The teacher that teaches us to draw told us to use the end of the pencil, then easily move it around a bit, while having the shadows held with more grip, and more pressure, and shading less and less grip and pressure.
Excuse my grammar, if there are mistakes.