Hi Everett: Thought I might add a bit to the discussion here. In your initial post you mentioned leveling sand. FA-2 (torpedo) sand is for the bedding course on brick patios. You should not be using sand for any part of a wall base. Gravel for wall bases in Northwest Indiana should be what is commonly referred to as "Grade 8", also designated as CA-6. This is compactable gravel for the entire wall base. There would be no sand and no other gravel in the base portion. Base compaction is normally done in 2" lifts unless you have an industrial compactor. To echo Revolutionary Gardens comment, using a hand tamper will not be satisfactory to compact the base. Rent the biggest compactor you can handle. The gravel behind the wall (between the wall and the patio should be what is commonly referred to as "3/4 Clean", also designated as CA-7. This is free draining gravel and would be behind 100% of all walls we build, whether they are modular like yours or natural stone like the photo below. Free draining gravel eliminates hydrostatic pressure and surcharge, which means your wall will not tip. Your wall height is such that 4-6" behind the wall should be satisfactory. On the outcropping wall in the photo below you can see the space behind the wall during construction. This is where the CA-7 goes. From one NW Hoosier (formerly) to another......good luck with your project.

Why wouldn't you put them both centered on the wall? You don't say what size fireplace you are getting but once you get the firebox installed and stone/tile around it you will probably close to 7 feet for any reasonably sized fireplace. If I did the fireplace on the side with very little tile around it, I would use the other side for a tall shelf and still center the TV above the FP. Personally I don't think putting a TV above a heat source is a good idea, but that probably depends on how much you use the fireplace. If you have the fireplace picked out or any drawings of what you are thinking about, post them here so more people can help you. The more details you can offer the better feedback you will get.

You have a great sense of color and proportion and it connects these two lovely and relaxing rooms. I think a gallery wall would muck this up. The size of your mirror is spot on and you are right, you will likely break the bank and drive yourself crazy trying to find good art that size. It is needle in a haystack hunting. I'd make finding that piece your five year goal. And, in the mean time do either of these as an in between phase to retain the great size of that mirror: A.) Try a faux mercury finish on the mirror to tone down the brightness and add a small sculptural doo-dads on each side like sconces or matching plates or chunks of aged wood. (Excuse my horrible attempt at replicating faux mercury glass!) B.) See if you can remove the mirrors from the black frame and use the frame to surround some nice wallpaper to use as temporary art. Lastly, please don't add colorful accents to this space in which you have mastered calm, warm neutrals. It is heavenly. What paint color is on your walls?

Triptych seems really choppy to me on that wall. You already have the two door frames cutting into the space. Across from it you have all of the many, many rectangular windows. The room would benefit from one large piece hanging here and breaking through all the vertical rectangles.