The first thing that comes to mind, if I were trying to criticize, is the back row against the rear wall. Now, a lot of people do that, when in a living room, etc. But, if a dedicated HT designer saw that, that might be the first thing they mention as well.
Also, I would not only try to mount the center speaker as close as you can to the display in that setup, I would also try to see if there was a possibility in having it angled upward. Mine is worse off, on the floor, but at least sitting on an acoustic panel, on top of rug, on top of carpet, angled up. Its flush with the display, and is the best I can do. For now, anyways.
Next, I would recommend room treatments. Bass trapping in the corners, etc, and treating of first reflection points.
Oh, yeah, since this is a truly dedicated setup, I think white is the worst color to pick. Darker is better. Black is best. Ideal is to immerse yourself in a sea of black, where the ONLY thing you see is the video. Hard to pull off.
FWIW, those are my comments. You can do only what you can do . . .