Where are you located? The reason I'm asking is because North Dakota experiences a much more severe winter than Miami Florida so your winter prep would be different based on your area.
For winterizing a coop, you ideally want to have all the openings high up above the birds so it can ventilate moisture (they expel a lot more moisture than you realize) and the ammonia from their droppings, without having them constantly exposed to direct winds and keep them dry. Lots of ventilation, but not direct exposure to it. The coop in the photo looks like it would have them directly in front of a large opening, exposing them to wind and possibly allowing blowing rain or snow to build up inside. I can't tell if that open side can be closed.
They will grow thicker feathers for colder temps and shed them (molt) in the spring, so you don't need to heat the coop. Just keep them dry. They are much more rugged than people believe and will survive sub-zero temps just like wild birds that live outside.
You will need to keep their water from freezing. Lots of ideas on this site for how to do that.
Raising that coop would definitely help if you get a lot of snow. They don't always like walking around in the snow and may decide to stay in the coop when the ground is covered. You could put it on a platform with a plywood floor, then cover the floor with pine shavings, then have a ramp going from the door down to the ground for them to walk in/out. All depends on your weather and budget.
For a floor covering, you want something easy to clean that won't retain water. Pine shavings can be purchased in bales at
Tractor Supply. 1 bale expands to cover a huge area and cost like $6. My coop is 16'x12' and I cover my floor with it. 6 bales last a year, but I built something to catch their droppings while they are sleeping so this helps make the shavings last longer since I have 30 birds pooping all night long. For just a few birds, the shavings will last a long length of time and help absorb the moisture from their droppings and minor water drips/spills to preserve the wood floor. Some people also use cheap linoleum flooring over the plywood as an additional lay of protection. Pine shavings are cheap, easy to clean, and easy to throw away. Straw or hay can be used, but some don't recommend it because the hollow shaft of the straw can be a place for mites and other parasites to live. They will live in the straw and vacation on your chickens. Sand can be used too, as long as it is set up to quickly drain water. Droppings can be sifted out of sand like a cat little box.
I can't think of anything else at the moment. During the coldest months, I remember my biggest concern was keeping the water thawed out and collecting the eggs before they froze.