The Gemara in Masechet Hagiga (5a) teaches that it is forbidden to do something that revolts one's fellow. The examples given include expectorating or killing a bug in somebody's presence. A modern-day example would be leaving one's used tissues on the table. The Gemara warns that one is liable to punishment for such behavior, for doing things that cause others to feel revolted.
By the same token, one is obligated to clean up after himself after using the restroom, to ensure that no filth is left behind that will revolt those who use the restroom after him. This applies both to public restrooms and to the restrooms in one's home which he shares with his family members.
More generally, one should always make a point of cleaning up after himself so that he does not cause discomfort to other people. If a person brings a cup of coffee into the Bet Midrash, for example, he should not leave his dirty cup on the table when he leaves. A person who uses the Mikveh should make sure not to leave behind any mess. We all have a responsibility to create a pleasant environment for the people around us, and to avoid creating an unpleasant environment. This obligation not only governs the way we are to talk to people, but also requires us to maintain cleanliness for the benefit of the people around us.