I like what's already been suggested (sofa on wallpaper wall and more closed storage).

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I'd hang your guitar on the radiator wall to serve as an art statement as well as keep it off the floor (just pull it down when you want to play).

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Pop some color with the bookcases ( https://www.ikea.com/us/en/catalog/products/80385616/ ) flanking the radiator wall in those niches. You can use wrapping paper or wallpaper to cover the glass.

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Throw a big white shag run in front of the sofa, and a plant somewhere.

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If you have the budget, I love the Ikea adjustable height desks. You lose drawers, but you will have the bookcases and vertical shelving. https://www.ikea.com/us/en/catalog/products/S29022520/ You could use another floater shelf to create the look of a long desk for you and hubs, but obviously it will look a bit weird if the desks aren't at the same height, so maybe skip that and just place your grey file cabinet between them.

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I'm in IT and my first thought was clearing some clutter from the desk itself (make a nicer work environment). There are dual-monitor stands for low prices now (https://www.amazon.com/VIVO-Standing-Bolt-through-Adjustable-STAND-V002F/dp/B00C5H5DN0) that can create space on the desk since that stand attaches to the back of the desk, and you can adjust the height so you won't have the additional strain on your necks.

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Use some of that empty vertical space with floating shelves and do under-shelf/cabinet lighting so you can see what's on your desk. Definitely, invest in some task lighting and cable management (even just double-sided velcro and 3M hooks work well). I'd suggest (unless you just bought them) replacing your printers with wireless ones so you can put the printer on the new shelving you just hung (not bookcases unless the doors are always open; you don't want the printers to overheat or cause a fire hazard) but can still easily access them when needed.

Good luck!