This study shows that stereotyping by whites drops if the environment is orderly. The implication for people wanting to increase the comfort level among races is conservative: you need to maintain a clean, safe living space. That means that cops, not graffiti, must seen as cool.
On the other hand, disorderliness may be an accurate and important signal of risk. It doesn't make sense to clean up an environment if it tricks people into being comfortable in an objectively dangerous place.
Another point: In one experiment, whites sat as close to a black confederate as a white one, as long as the scene was clean and orderly. Does this square with the whites-as-natural-haters meme that they would sit just as close to a strange black man as a white one?
H/T Jason Malloy