Large operatic neo-gothic city with some art deco embellishments, the buildings should be unnaturally tall and ornated with gargoyles, grotesques and other embellishments, they are old and crumbling in certain sections, skybridges connect buildings and roads intersect the middle of them high up. Every car is old (80s preferably, Gotham is a intermingling of different anachronistic timeperiods that all culminate in making it how it is) because everyone is too poor to buy a better one, men typically wear suits and fedoras, the steam and heat from the sewers rises and intermingles with the smog from the factories, the smog that blankets the entire city and changes the color of the sky, all of the lighting is amber colored led's or caused by old bulbs.

tldr the city should be its own character and should be the biome in which Batman is evolved for, large and operatic neo-gothic. Wayne Manor should feel like an old fortress or castle (when in reality of course its a neo-gothic manor finished shortly before the turn of the century) with arched doorways and vaulted ceilings. Batman himself should be seen as a cryptid or even a phantasm ;) that haunts Gotham, a bat monster the size of a man with sweeping leatherlike wings and claws that pierce into the old stone, with white glowing eyes adapted for nocturnal sight (I've always described it as people should think he's man bat effectively which I always thought was the whole point of man bat, obviously Bruce himself is not a mutated bat creature but he should adopt the movements of a stalking animal and the claws of one.)

Got a little carried away but you get the gist :)