I believe I understand what you are taking about. I have seen some cars with good texturing but the car it self looks more like a toy model because of the lack of details overall. I do have some gray model cars if you like I can post it up. and you can give me some tips. if it's not too much.

i think on a car the modeling prosses is the most important to make all the details and gett a realistick feel overal. the material is just a finish tuch to make the car belivable and nice inn the render.

but a car can look awsom in grey if it is great modeled.

hope it made sense :P

there aint much texturing involved in cars. it depends more on materials. a good material is important to achieve a good looking result. a scene can be as easy as a photo. as inn the tire and rims render you have.