For your living room I wanted to create a space that is both functional and cozy. I kept your sectional in the corner against the broom closet. I think this is the best placement for the optimal space saving floor-plan. I added two accent chairs that will provide more seating and they help section in the seating area of the living room for the ultimate cozy feel. A small accent table between the two chairs will serve as a place to sit drinks or other things you might need. Then I softened the boxiness of the room with a round coffee table.
On the left side of the fireplace I added a small console to conceal all your media equipment. This also adds a surface for decor in that corner as well. Next to the sofa in that corner I added a basket for throws. Having lots of throws helps add texture and coziness. I also added a rug to the living room to help ground this area and provide a distinct space in your open concept. In the right corner of the room near the fireplace I added a floor lamp. (Accent lighting is key in making a space feel welcoming and cozy- a couple table top lamps will be used in the design as well). I kept the area behind the accent chairs open for walking and flow.
Next to the french doors I added console table to help balance the furniture in the space and to serve as a catch all from entering/exiting through the sunroom. I also added a rug and plant. Over all I did not add a ton of furniture because you do not what to overcrowd the space. Each piece serves purpose and balance.