In its most significant sense, mise-en-scene refers to everything under the control of the director, that is, the aggregate effect created by art direction, placement and movement of camera and actors, lighting, and other visual elements in a given scene. In other words, mise-en-scene is what the director does. By extension, but somewhat more vaguely, mise-en-scene can refer to the dominant visual features of a film or film genre, e.g., the typically cramped, somber mise-en-scene of the film noir.

-- Straight Dope

Directors may take credit for all this, and a minority might deserve to, but . . .