Rather than ranks, I'd like to think that if you work with clients for card or game illustration, you're a drafter not an art director. So, your work is to deliver the art that clients want, and you must listen to their direction no matter what. If you're an art director, your job is to define the aesthetic and style of the project. This is where you can use your sense and idealism. Lastly, if you're famous, you can make whatever and people will still buy your thing. It's more like class/job in rpg, It's either you're drafter, art director, or famous.