That kind of concept art is not for the level designers. It's for the executives, art directors, and creative leads to help figure out what the overall visual target of the game should be. The designers don't use traditional concept art. Usually they graybox things directly in the game, or via something like Sketchup. Some…
Have you ever played the original Star Wars: Dark Forces game? That and the sequel had some pretty intense level design, especially compared with newer titles. Put that sort of thing in a game these days and people would complain about getting lost and how arbitrarily the keyhunts pad the game play. Would they be right?…