Random thoughts:
I love that background...except I find the juxtaposition of vertical and horizontal "seams" very jarring. Personally, I'd much prefer all one or all the other; for your vertical tank I think the vertical seams would be preferable, IMHO. Depending upon the size of the sheets, maybe you could cut the background at an angle so that the slabs of rock appear to be leaning one way? Play around with it.
Putting about as much thought into your substrate colour choice as I have put...
in total...into all my substrates for the past half century
...I think you need a mix of Redwood, Spiced Cedar and a bit of Baltic Brown. I gotta admit that I feel a little bit silly even typing that...
Once upon a time, I experimented with an all-glass tank, which also had an exterior photo background. I laid it on its back, poured a few small puddles of clear epoxy on the back panel here and there, and sprinkled those spots with some of the same sand that was used for the substrate. I found that it really helped to blend the background and substrate and also provided a wee bit of a 3D look to the tank overall. With the background you have chosen, it would also soften all those hard visible joints and edges.
IMHO, you are getting unbelievably carried away with the concrete supports. That setup as shown not only removes any chance of undertank storage (and I get that you are not concerned with that...) but it's gotten to the point where you won't even be able to get your hand under there to retrieve a jumped fish, or roust out a wayward spider. It's bordering on a solid concrete pylon! Ease up a bit!
I can't help but mention that a strong enough top would allow you to simply have a column in each corner while supporting the entire floor of the tank. Those columns could consist of vertically stacked blocks, rather than horizontal. You'd use one or two blocks per corner, not a truckload like that drawing calls for.
Yes, yes, I know...someone will immediately pipe up and say "No! Don't do that! The blocks must be oriented with the openings facing up/down, with no gaps visible or accessible!" While it's true that the maximum strength is obtained that way, the simple fact is that these blocks are astronomically stronger than required for this application, even when placed the "wrong" way. Enough is enough; too much is just silly and wasteful. Placing the blocks "incorrectly" will leave a beautiful big space under there allowing for the immediate or future installation of a sump (preferable) or even one of those horrid canisters over which so many people swoon.
Excellent to hear that you have considered the usable space in the tank; you can definitely find fish species that will use some of that possibly-barren upper part of the tank, although maybe not with the fish you have already chosen. But all is not lost; if you snoop and search around enough you should be able to find some sort of long driftwood decor that can be mounted vertically, and that will provide some much-needed "vertical substrate" for many fish. A piece like that can, if waterlogged, simply be placed on the bottom so that it projects upwards. Another great way to use one is to use some sort of clip or zip-tie construction to attach it to the tank's top rim or crossbrace; once you find just the right placement, you can saw off the part that sticks above the water surface so that it doesn't interfere with the tank cover. You'd be well-advised to have the background sorted out and installed before playing with the orientation of the wood to make sure the two don't create a jarring effect together. Lots of "bottom-oriented" fish are, in reality, "structure-oriented" and a vertical piece hanging over their heads makes them comfortable using the entire tank depth.
Painted pineapples? Hydrangeas? Mums...crocuses...hot pink...?!?!?!? Hey...it's your tank...
Just a few suggestions and ideas, purchase price cheerfully refunded if you don't use any of 'em.