I'd go for the Switchgrasses because except for a couple months after trimming in spring, they are ornamental all year. Look them up and check out the different cultivars. They sway in the slightest breeze, are easy to cut back in spring, bloom early so you get those great seed heads with the sun coming through them for a very long period and they stay upright in winter. The best ones (I think) are Heavy Metal and Northwind. For fall color, there are the red ones but in my mind they aren't as pretty in summer. Too much moisture makes some of them flop but these two I mentioned never seem to. Seeding is minimal.

Another good one is Muhlenbergia lindheirmerii. Tall, blueish and thick. Santa Rosa Gardens carries it along with several Panicum (switchgrass). Those 4" pots quickly grow into gallon size.

I planted a row of Sacaton wrightii from seed I purchased from Plants of the Southwest. It has great seed heads all summer into fall and is one of the best for that, they seem to glow. Its a very large grass but would take two seasons from seed to see results.

Indian grass is only ornamental in fall. Same with Big Bluestem. I would not count on them to carry the show. Little Bluestem is a much better choice for being decorative over a long period IMO.

Look at High Country Gardens website. They have that 'Flamingo' Muhly and Muhly riverchonnii (Oklahoma native) too. Those are both great grasses and very decorative, the 'Flamingo' has slick, metallic blue, rolled leaves, so its just gorgeous for color contrast even without the pink blooms. Neither of these seem to seed at all unless you get lucky.

TexasRanger, thanks for the suggestions, I was hoping you'd chime in on this. Your comment about The Blues got me thinking about this again. I'll take a serious look at the switchgrasses -- I like the idea of panicles since the prairie dropseed ones look so good in the morning light on the other side of my property.

Pink Flamingo muhly is interesting -- I think I have been assuming until now that I'm too far north (or my soil too heavy) for muhly to do well. I wonder how it would do when we have the occasional deep freeze.

At this point my main concern is for late fall and winter. It's then that the view toward the back neighbor seems the bleakest and I was thinking the grasses might help cheer things up a bit. It's important that they stay in good upright form as long as possible and not get crushed down by snows.

We got down to 3 degrees last winter when that vortex business came through and it was an unusually cold winter over all. So, I'd say last winter was a very good cold hardiness test, both 'Flamingo' & Gulf Muhly's did just fine, all the muhly's did. I doubt they would like real wet in winter but I cannot comment on that from experience.

Pink Flamingo blooms late and comparatively briefly, I'm still waiting on it but I only have one as a specimen. The switch grasses on the other hand bloom for me in late June - early July and glow all summer so you get more "backlighting time" if you get my drift. I planted mine in groups of three and have more started from rooted sections I dug out to plant more. I love the way it looks in moonlight too.

I just came back from the store, I saw a whole row of some other kind of switch grass that had deep pinkish blooms and contrasting green leaves. Wow, what a sight it was massed in! I have no idea what kind it was. Oh, by the way, they don't resent wet feet either.

The P. 'Northwind' has contrasting yellow blooms against the dark olive green leaves and its nice too. They give the colors online so you might want to just take some time and read up. I love them.

I would also recommend Panicum vir. "Heavy Metal" as it is my favorite upright grass. Fall color exceptional. Depending on the chosen density of your grass 'wall' consider Mis. sin. 'Yaku Jima', 4h 4w and dense w/ airy plumes when set.

As others have stated remember grasses should be cut back in spring therefore your living wall will be gone for 2-3 months.