I was thinking of an aqua blue with the lime-ish green and silver you have already determined you will use. Would be a little calming with the brighter elements. You can sometimes find smaller, inexpensive upholstered chairs all over the place....overstock, Pier 1, Wayfair, etc. I would also make sure you used those colors in the rug and maybe a pillow or other decorative pieces.

You could install on the ceiling even if there's not a j-box, I've seen many homes and condos where there's lighting on the ceiling and connected like a swag fixture (long cord to an existing wall outlet). If interested I do make custom lighting based on the client's specifications. Feel free to request a no-cost quote at: Retro Steam Works / Custom Lighting Design PS. I did that on my son's room, where we installed a chandelier and connected it to a wall outlet (controlled by a wall switch).

II like the desk entirely hidden behind that wall, but this is better for Zoom calls. You need to be facing a window for the natural light to be on your face. You can use a ring light on cloudy/rainy days but if it is sunny, use the natural light. That also leaves the wall to your left for a new office storage piece like a credenza or file cabinet. If the glare from those windows bothers you when working, get some custom bamboo shades at Lowe's in a shade that picks up the caramel color in the rug. A new ceiling lamp and a brass floor lamp for the corner by the sofa will look great.Move the round brass table to the entry side of the sofa for a bit of bling to be seen as one comes into the space. Also add a lamp to your desk. Try not to use the ceiling light, for a warm and cozy feeling. Ceiling lights are great for seeing how to clean the space, but they do not enhance the ambiance unless they are interesting to look at. And speaking of visual interest, the map isn't that. If you need it for your work tasks, move it close to the desk. I would be something fun and colorful to hang 5" above the sofa. Don't forget a trash basked if you don't have a shredder.

As is, about the only option is to hang curtains or shades from the ceiling. As msjoan noted, there isn't anything to hang a door on because there is no framing and no room to add framing. So, basically you need to decide whether you want cabinet type doors or bipass or bifold or swing doors. Tear out what is there, carefully, because you can reuse some of the material, and proceed from there.