Hmm. With the gray, I would go with dark flagstones. But that's just me - I like the dramatic look.
And the brick wall may not be completely useless - I like M.B.'s suggestion of a bench w/ a planter, and there are lots of places where you can get artwork that can go outside. Or try a trellis with a flowering, thornless climbing plant. (Honeysuckle, trumpet vine, or jasmine, maybe?) Any of those vines you would want in a pot, anyway - once they get hold, they go EVERYWHERE, and being restricted to a pot helps them be less invasive.
Blocking the apartments....hmm. Since you are building beds, anyway, you could build one for bamboo. You'd want to build a bed for it, I think - it's a grass, and it propogates by runners. It'll be all over the place, if you don't restrict it to a bed. Otherwise, you'd do best to ask the folks at a garden center or plant nursery..people who love plants. They'll know what you need for a small space that does well locally. The benefit of having a local plant is that it's a whole lot easier to take care of.