How about training some pear or apple trees in espalier?

You can also add an evergreen vine. My Bower Vine tends to grow fairly upright and not go past 4' in width, but it has pretty, shiny foliage and produces beautiful white flowers.

Also, have you given any thought to a clumping bamboo? The running bamboo is certainly to big for your yard, but the clumping might be able to stay within the confines of your area.