the poster is cool but you have to remember that the image as a whole has to flow. not one piece can distract from another. also you dont want it to be to cluttered.
my teacher once told that you want your audience to look at your poster in a clockwise or counter clockwise rotation. both posters above demonstrate that beautifully. star trek one you look at captain kirk then spock then the girl (no clue who that is) then the ship blowing up the other ship then back to Kirk.
Iron man is the same direction.
Iron mans face then his glowie thing then the black guy ( i need to watch these movies) then the girl, the fight scene or the old man (that a good distraction the make you look at poster 2x) then Stark then iron man again.
its all about the flow.