Storage, especially in a small space is not only appreciated, but necessary. And while you can't add closets, what you can add are shelves. If a little extra storage is just the finishing touch your small space needs, consider adding shelves in one of these unexpected places. Bonus points for the renter-friendly solution to your storage problems.
Home Organization: Stairs doubling as drawers. Modify your stairs so that each step can also hold a drawer for extra storage of all your stuff. The things you put inside would have to be of the occasional-to-rare use since these look like a pain to have to deal with on a regular basis.
Command hooks are serious life savers, because they offer a storage solution for items that otherwise are too oddly shaped to stay put on their own, like these mixer arms. See more at The Hyper House »