Octagon shaped will help eliminate blind spots. I'm building the next two 6' deep x 7' wide. It's not a "true" octagon since the front and back are wider. Like everyone else has said, awning over windows and doors. Carpet on the floor and walls. Insulation on walls, floor and roof.

Shelves are a must however, attach a drink holder and binocular holder on the arms of the chair's. This will minimize your movement reaching over to a shelf. I dip and keep my spit bottle right on the side of the chair.

20# propane bottle mounted on the outside with hose attached to buddy heater. Don't have to worry about running out of gas during the last hour of the hunt and having to change the bottle.

Thin carpet on all of the shelves to minimize noise.

12v battery mounted outside with solar charger and cigarette lighter plugs on each side of shooting house. You can use it to charge phones, small coffee pot or water heater for hot chocolate or Ramen noodles. Also, a couple of green lights mounted under your shelves to help you see getting in the stand and when packing up to leave.

Sleeping bag in a big ziplock bag to keep in the shooting house. This is great if you take kids, a wife who doesn't like the cold when the windows are open, or if you want to take a nap on one of those miserably cold days.

Now this next one is a life saver when you want to stay in the stand all day. I keep a 5 gallon bucket in all of my shooting houses w/trash bags to use as trash can. But here is the real reason, it doubles as a Porta potty. I buy a cheap toilet seat, attach some small wood blocks on the bottom side that allows it to fit snug onto the 5 gallon bucket. Next, I keep a roll of the thickest trash bags I can find and double bag the bucket when I have to take a dump. When finished, tie the bag up tight and you won't smell it. I keep the toilet seat hung on the wall and a bungee cord to keep it snug in case you bump it with your chair.