Take a look at my brushes in the Elements section. The closest thing that I've ever come up with is in there called the house brush and the thatch brush but you need some paths for it to work (that part is in my town tutorial). It basically takes a square brush tip and sets a size jitter, rotation jitter, roundness jitter, and increased spacing. The roundness jitter makes the square into random rectangles, the rotation jitter makes them all slightly differently aligned to a path, and size (of course) makes em various sizes. For convenience, the brushes and tuts are in my sig.