I like to carpet the window sills and the floor to make it quieter. A comfortable chair is good. A few nails to hang binos and stuff. I carry a buddy heater on brutal cold mornings. But that's not actually an accessory to the house. I like to use a sid panel plywood window that hinges from the top. It also doubles as a sunshade and rain diverter. A piece of paracord is used to open and secure it. That's about it.