To gain some more inspiration for this brief I read over the summery of the film again and remembered it is set in San Francisco.
Looking at some images of the city on the web I found this image and thought the climber looked a lot like an ape.
The location is something that sets this 'planet of the apes' move apart from the others and could provide a focal point for the poster.
I have drawn up a minimal vector of the bridge based on late travel poster.