I would buy the largest rug possible for the area with the sectional which will help to "pull out" the sofa from that corner. Something with a bit of color to liven up the monochromatic look of the wall and sectional would really help. Instead of red I would consider yellow or lime green pillows, and also pillows with more colors and patterns. I don't see any lighting in that corner which gives it a rather "dead" look. A tall lamp to the left of the sectional would add height to that area in addition to light. Since the mantel already has a shelf-like look, I'm not sure whether shelves are the best idea. They should at least look very different in design and I would paint them the color of the wall. That will make whatever you put on them really stand out. It's a very nice room otherwise. If you like art, a beautiful picture over the mantel would make that area more of a focal point.

If you have lots of art try some on either side of the fireplace, remove that mantel and get one in a wood similar to the table and add some proper trim around the fireplace. The mantel is too high to do much for decor. It seems odd to have the fireplace in this narrow DR was it something else before ? Some nice window coverings , remove the stacked tables in the corner and the clutter from the ledge.When doing the art just keep working at what works well together and I would google how to hang multiple art on a wall.I don’t love gallery walls but sometimes they do the trick if done right.

Taking possession of our new apartment. Looking for recommendations on how to decorate and layout of the main living area. Looking for recommendations on colour to paint the walls, as well as how to place furniture. Thank you!

If you are keeping your furniture, I would also keep the wall color, which works well with your floors and the blue sofa. I would add a large rug to the living area, in a pattern that incorporates a small amount fo the blue color. The biggest way to update your space is with new artwork. You need larger pieces, or you could try grouping them together. You want art to be hung at eye level when standing. You could try using the largest blue piece on the back wall and grouping all the rest over the sofa. Or keeping the blue one over the sofa and grouping everything else on the back wall with the mirror. Will you have a tv on the console? You could paint just that wall a deep color if so.