First of all, the deer heads should be grouped together with the largest head in the center and a few inches higher. They are all too close to the ceiling. The other wall
hangings are scattered and need grouping as well. Furniture placement is bad and
needs to be reorganized as noted in the previous comments made. The future
fireplace should be centered between the two windows. If you are planning to buy
new furniture, two sofas pulled towards the center of the room with a padded ottoman/
table would work very well. Storage inside this table is also helpful. Area rug, absolutely. Window treatments should be blackout type,so not to glare at you when you're trying to watch tv during the day. Not critisizing, just trying to be helpful.

with such a big room you don't need to have the furniture smashed on walls. bring that sofa to the middle of the room facing the tv. place it far enough back to add the table and area rug. pull that chair to the either side of the rug end nearby. add window treatments and lower the dead animal displays they're just inches from being dangled from the ceiling.

Two ways to add coziness: first, a very large area rug to cover the entire seating section; then, some floor length, straight drapery panels. If you attach the rods carefully, outside the window frames, the drapes won't block the light. If you really don't like drapes, you could try roman shades, but they're not nearly as cozy.