Concept artist is what you are looking for I think. How to get there... I dont really know. But the number one tool for them is probbaly Photoshop.
Concept artist think of the global desgin of a level, mostly they create to global look of a hole game. So they are also desiging the look of the buildings in the games.
I readed a article about concept art in games and how it affects games. In there was that concept artist stay in the production line the whole time. They have to change things if they dont work out in the 3D section.
I hope this helps a bitt, if you not please ask.