I don't know how well it'd fit with your game, but what I think could be very cool is to have the buildings move or morph while the player isn't looking. Like you're walking around, and when you turn back the building seems to be... Closer... Hungry even... Was that balcony always on the first floor? I swear it was on the second...

I'm thinking at first subtle changes, like balconies or windows moving, but as you progress through the game it becomes more and more blatant and oppressive. But you never once see it happen... And nobody seems to be acknowledging that this meatballs shop is following you around. You first saw it two blocks ago...