My brother and I built our coop and run. It is insulated and during the winter we enclose and insulate the run as well. We built it originally to have 15 hens, but we have about 40 and a couple of Tom turkeys as well. They fit in very comfortably at night and during the day they free range, so they only go in for laying eggs or grabbing a bite and a drink.
We use sand for the flooring and in the winter I use hay or straw on the floor to keep in the warmth.
I had posters and pictures hanging in the coop originally and the nesting boxes were storage containers from Menards.