I would make the fireplace room the living room. Remove everything…bookcases…everything. Two sofas, legs showing and neat arms, positioned perpindicular to the fireplace with a small rug under a glass and iron rectangular coffee table. Left of the fireplace in the inspiration photo, is art work. I would do one on each side of your fireplace and a mirror over mantel. Shop for a pair…that way size and frames and mats will be the same, but art will be different, but same subject. Make a dining room out of the space with the big rug, which looks like an 8 x 10, which is perfect size for a table and chairs.

At that height, I don't think it is a chair rail, it is a picture rail. Those are unique antique fixtures and hard to come by. I wouldn't remove, but I would not have a separate color for the lower half. I would consider the wall all one and paint it all the same, and then use the picture rail to hang the boards. Does not really matter how you paint, either light or dark. Lighting and window will make most difference in how "light" the room is. Vibrant colors can also make a room feel more cheery, if not "lighter." Up to you which way to go. A little green can go a long way, you might consider some plants. I hate watering them and have a tendency to kill indoor plants, even though I am a horticulturalist. I am like the plumber who always has a leaky faucet at home. I tend to ignore my houseplants. So your idea of an accent wall with some greenery might be a really nice and easy way to make the office a fun space.

Thanks for the great tips. Yes, it's a good point that 16 won't be sitting at the same time...more like 12 or so. Sadly, I have to go fairly dark due to the cleaning and staining issues. I should have added that I plan to add a large 12 x 15 area rug to break up the dark sofas from the darkish wood. I can't go with medium gray because it will look too "matchy-matchy" with the med. gray stone fireplace. Quick question/concern...I searched for sofas that are made from "Sunbrella" people here suggested and there are only a few and they are outdoor sofas. Mostly, the Sunbrella fabric is pillows. Also, I'll be removing both sofa tables behind the sofas that are there now, so that will give me another~ 4+ feet. But I still plan on putting more narrow sofa tables as I don't want the sofas right up against the walls, so it will be more like an extra 2 feet I'll be gaining. Any other suggestions for a "tough" fabric that won't be torn easily? We've had issues with guests sitting on the sofas, etc., with keys, etc, in their back pockets that tear the fabric or snag it. What are opinions on leather? Vinyl? Also, I'd like to lighten up the room with a cleaner, more modern white (ish) paint, maybe with a touch of gray, )but not with any blue or "pink" in it.) The walls are now painted Sherwin-Williams "Accessible Beige" and the Doors (not seen in the pictures are "Dovetail"...which I LOVE, but is way too dark for the walls. I've already gone down the line of the "Dovetail" paint strip and the lighter colors look kinda "pink-ish" in that room.) Thanks again everyone

For decorating using light colors definitely brighten a room. Other design options are adding a mirror on the opposite wall if possible to the window to reflect light back into the room. Add mirrored furniture & accessories also for reflecting light or light or ghost furniture to remove weight from the room. Keep accessories light. Adding artificial light will definitely help. A pendant light / chandelier which is glass will cast more light than and a heavy shade. Window dressings should be light so perhaps paint your wood. Dark colors at the window will absorb light coming into the room. Task lighting ie table or floor lamps give functionality plus look like purposeful design. So whilst your waiting for the electrician there are still ways to lighten the room. Even though it is dark you are on the right track to making the room cozy with your rug and walls.