so iv been reading over TKJ and im thinking of making like a darker batman trailer, taking some of TKJ elements (the opening arkham speech, joker shooting barbera) but what makes a creepy atmosphere? iv got sounds like that hissing smoke and back alley water dropping and dark shots

I might consider using an otherwise everyday sound that fits with the material in an appropriate manner and use it several times in the video; i.e. heartbeat, camera snapshot, footsteps, sighing. Among the creepiest things to me in life is when something previously considered harmless gets married suddenly to something sinister, like, for instance, laughing.