One of the most put-together looks in a room's design is matching the window treatments and the walls. Repeating a fabric in both places creates unity, but it also requires a careful approach. When the walls are completely covered with a busy print that's fully repeated at the windows, the effect can end up resembling a motel room -- a space with not much character.
What's more, the room can unpleasantly encroach on our vision; no diversion is present to attract the eye. A better solution is to break up a single pattern by introducing another print or solid. This can be done on the walls, with one pattern above the chair-rail molding and another below, or with a different border print.
Breaking up too much of a good thing at the windows can be done with a literal break in the pattern -- a valance can be followed by bare window for several inches before the curtain picks up again. Or a multifaceted window treatment can incorporate more than one print. The important safeguard to keep in mind is avoiding too much of one thing.