I can't believe nobody else can imagine a HUGE MOFO of a Mothership coming up from behind us casting the shadows on those buildings! I certainly can! Not everything has to be in the picture for it to conjure up the feeling of dread! He could also be showing the view from the twin towers as they're throwing up a cloud of smoke. My tip would be to add something to the edge of the field of vision to suggest that something big is going on behind the viewer! Papers in the wind? Flames? Smoke? What have you.