Maybe start by looking into a nice, soothing shade of blue-green, like Sherwin-Williams' "Watery" or "Tidewater," depending on the lighting in that room. A blue-green is a bit more modern but will still help with productivity and also be nice for guests when the room is goes back to being a guest room. I'd also paint both doors white (looks like door on the right it already there). It also looks like you could potentially put some art or something for visual interest on the right-hand wall behind you.

I don't think it's unprofessional, either. The whiter background makes the room look like less of a dark hole, but better lighting might accomplish that more easily. Whites and neutrals can be kind of fickle when it comes to lighting (artificial and natural, with variation from your room orientation and what's outside your windows). You might look at Benjamin Moore Pale Oak, which is a pale warm gray.

If you don't use the closet often, you could hang curtains to create the illusion of a window (curtains always closed, obviously)

I have a temporary office set up in my kitchen with the fridge in the background and excessive backlighting from the three windows. You have me beat by a mile.

After trying several colors, I settled on Colony Buff by Sherwin Williams. I would suggest you use it on all the walls and paint both doors and the trim Extra White, also Sherwin Williams. Is the mirror on the left attached to something or could it be raised? Also, the lamp could be taller and have a pure white shade and daylight bulb so that it doesn’t look yellow. You don’t necessarily have to buy a new lamp, just set it on some books. A colorful piece of art on the right wall would be nice. Doesn’t have to be expensive. If you have a Home Goods store near by, they usually have a good selection. Finally, I highly recommend that you set your computer or phone so that the camera is eye level. Your face looking forward and not down will look more professional. For my laptop, I just set it on four reams of paper to get it high enough. For a phone, there are simple stand available on Amazon, some inside of ring lights that help illuminate your face evenly.

The lighter you paint the walls, the more your ceiling needs a fresh coat too. Also, are you home alone when working? Anyone that might pop in for something while you’re conferencing? Is that the only spot your computer can go…facing a door?

Go outside? There’s no replacement for Gods creation. Beautiful. Tops any designer’s room.