Accent lighting appears to be missing; your idea of a floor lamp at end of sofa is good. I think an arc lamp would be a bit overpowering--there are plenty of other transitional options--and lots of suggestions from houzzers if you ask. I would also place a small drink table in this space and lose the basket. Other suggestions: Move the mirror---it is distracting and not working as others have noted. Perhaps in your entry? Scoot your sectional further away from the wall---it appears there is sufficient open floor space. Open space is good and will help your room breathe and appear larger. Panel drapes behind sofa and new drapes of the same on your slider would be my next move. Mount them outside of framing (so inside edge is at the framing) and much higher--almost to the ceiling--- creates illusion of more space in your room. Consider art for between these windows once panels up. Looks comfy--enjoy good times and memories in your home.

In the top picture, is the area off to the left meant to be the dining area? The sliding glass door to the deck is next to it so I'd like to still keep it fairly open. How often do use this sliding glass door if it has a curtain hanging over it? Is there another place you can feed the dog? If it were my house, which has lots of books : ), I'd be tempted to place several bookshelves along the wall, between the windows and to the right of the window at right. And a fabulous Persian/Oriental rug in front.

Start with a much longer media cabinet and place it flat on the wall opposite the sofa. If you like the TV on that end but angled, either place it on a swivel platform or mount it on the wall on an articulating arm. You might then even get a small chair in the space to create a conversation group which will cozy it up instantly. I do mean a small chair.

we need a straight on shot of the wall with the chairs. The tv needs to go on one of those walls possibly or so you can create a square shape in this layout. the end of the room with the exterior door and door way that part of the room should be treated as a pass through area . the game table might need a new home, I would wall mount the tv on a pull out so it can be angled for viewing and tucked back when not.