I personally like a sofa and two swivel chairs. That way, you can position the chairs where they are best for conversation, but they can turn toward the TV when needed.

I don’t think your furniture will fit in the dining area. Getting the mount would help with tv viewing, with the over fireplace placement and the placement of fireplace. Art is a very personal thing. You could hang some art on the wall behind the sofa. You could do one large piece or a couple of pieces or create a gallery wall. Etsy.com is a good resource for art - all types.

Nice space! If you could provide more details such as the style or color you prefer, the color and size of the sofa and whether you will be replacing the furniture... That would be wonderful and I believe there will be more specific advice for you from this warm forum. Here are some bits and pieces of advice, hope it can help a liittle: I noticed those curtain rods and if you have a need of filtering lights and protecting privacy, I would recommend blackout curtains. They can also add such a fresh touch to the space. For the sofa, I would suggest placing it in the corner, rugs and some other simple decors could make a lovely coner! Will the dining table and office desk be replaced? Here is some inspo if you need.

sell the couch and get one that works for the room and allows tw chairs opposite. Your fighting wth room with that sofa and that is why you can get a layout you like. I assume that is a 2 piece sofa. try taking away one peice and then play with the layout. also provide a floor plan and pictures of the whole room if possible.