If you decide you aren’t going to have the desk against a wall, put a floor outlet in now so that you don’t have cables running across the floor. I did a floor plan with my desk and rug then figured out where I would need sockets.

it will be more of a full-time office, but he travels a lot & visits clients frequently working out of their office What I like about Beverly's last suggestion with the worktop extended along the wall is that also gives your husband more storage for things like files, etc. Without something like that, will he have enough storage in the room? Otherwise I would strongly consider a credenza for storing files, under the TV, rather than a media console. For curtains, given your color preferences, these would be nice, https://www.potterybarn.com/products/haylie-print-drape/?pkey=ccurtains-drapes&isx=0.0.6515 I would also re-hang the curtain rods above the casing and extend them several inches beyond the casing for "stack back". If you opt to buy a rug from PB, exercise caution because historically they've had problems with rugs that smell (generally a "burned latex" odor). Make sure you get a *woven* rug, rather than a tufted rug, esp tufted rugs from India. There's a long thread here somewhere, and also this, https://rugchick.com/pottery-barn-rugs-to-run-from/

Try the art pieces with top one at the top of the window and then the other about 1.5"" below the first. Your other art looks low to me. They should be hung so the middle of the art is about eye level to you or at a height that is compatible with the art between the windows.

It wouldnt clash at all as long as you don't put them right next to eachother in the room. Mixing metals/wood tones is very "in" right now. All of your other elements you mentioned will balance it out.