9. A More Gothic Gotham
Batman '89 wouldn't have had nearly the impact it did if it weren't for the set designs made by renowned artist Anton Furst. Likewise, Batman: The Animated Series just wouldn't be as interesting or fun to watch if it looked like every other superhero show on the air at the time.
Gotham in those two incarnations was a gothic, art deco nightmare with different colored skies, buildings that make you think you're in bloodborne, blimps everywhere for some reason, and with a near constant layer of smog billowing into the sky. And yet ever since the Schumacher movies, the Batman films have been embarrassed to let Gotham be anything other than just Chicago.
The point here is that Gotham is just as important a character in the Batman mythos as Batman himself, so if we're going to spend multiple films in this one city, it had damn well better be an interesting city to live in. Gotham should feel like a city on the brink of madness, all the way down to the architecture of the place. It should look like the kind of place to give birth to the kind of insanity Batman fights every night.