what do you call the people who make cars look nice like adding rims ...etc?

[Erie]

the people who customize cars, like add rims and make the interior look nice by adding TV's on the seats, basically what the guys on the show pimp my ride do. i want to know what that job is called. i don't think its an auto mechanic, i mean don't those guys just fix your car like when you have a faulty light or something. well anyways i would just like to know what that job is called. if you know more about the job feel free to add more info thanks you