I will speak for myself. I am sure everyone has their opinions, preferences and personal experiences. I wasn’t until a year ago, when I purchased my current home that I felt that I finally had “my” ideal dedicated listening room. This room is for audio only. I have a separate room for video. Here’s a brief description.
The door is located behind the listening position. All of the walls are (almost) non-resonant brick. The only room in the house with brick walls inside and out. The rest of the rooms are brick outside and sheetrock inside. The foundation is concrete. The audio components are all in a recessed (former closet) located to the left of the listening position so that they don’t protrude into the room. I removed the closet door and put a thin light filtering curtain in its place. This allows for air circulation and also acts as an acoustic panel, while still allowing the signal from the remotes to penetrate and the pretty lights to slightly show through. I installed 6 30 amp breakers and ran 6 dedicated 10 gauge Romex wires and outlets in the closet. I duplicated the curtain on the right side, where there’s a window. By pure coincidence, both curtains ended up being symmetrical in relation to the room. I replaced the window with a soundproof window like the ones used near airports. The carpet is not thin or thick and the fibers are dense and very close together. Both the left and right walls are free of any obstructions, other than for the two curtains. All of the media (records, CD’s) is stored to the left and right of the door located behind the listening position. I have 3 recliners in the room. The one that’s centered with the speakers is where I sit and then I have 2 others that are slightly elevated to the left rear and to the right rear of the center listening position. The room leans more toward being live than neutral or dead, which is just how I wanted it. There are two bi amped tower speakers about 4’ from the front wall, 3’ from the side walls and about 8’ from each other. I keep them projecting straight ahead and not angled. There are 2 subs, one on each corner of the front wall. The front wall is bare brick.
Out of all this, I find that the best part is that the components are in the closet and the media is all behind me so that nothing is in between me and the speakers. You are fortunate to have a blank canvas! While your room is in construction, and if I can give you my humble advice, incorporate an opening to the left, right or behind you for your equipment and media, so they don’t get in the way of the sound and preinstall cables and wires in your walls. I couldn’t hide my wires and cables very well because of the preexisting brick walls. As far as any acoustic treatment, you can always finalize that after the room is built, but I would definitely build the walls and ceiling in as resonant less materials as you can afford, as well as a cathedral shaped ceiling and a concrete foundation. I hope that at least some of this helps. Congratulations!