Love your desk, E K. Is this going to be a ‘constantly in use’ home office? If so, practicality might direct your design choices. For instance, do you need task lighting? Or could a statement light fitting work? It’s proportionally suited to the room, so I’d keep any decor to one single piece or a group of three smaller pieces. For me, the style of desk seems suited to modern glass ornamentation. As for artwork, consider www.artbank.gov.au which allows you to lease beautiful Australian art or www.bluethumb.com.au which supports established and upcoming Australian artists and if budget is tight, go to your local auction houses. Unless space is very tight, consider leaving a space on your bookshelf for a colourful ceramic or sculptural piece, ensure there is some design or colour connection between your pieces, and I’d say your done

When you say nook, is it an actual nook with walls on three sides? I imagine it would not be very difficult to attach a supporting structure around the walls fixed through to the studs and mount the desk surface over it. If the desk is to float from only one wall that's a bit more complicated, and might depend on what weight it needs to hold.

Also if i can avoid moving air con for now that would be great. The next phase of reno will be to take down the wall between lounges and put aircon on the front wall of the lounge as it's the only other outside wall it can go on. Here might be my plan for now. I'll put the kitchen in place and figure out if i need to add more storage to office area. Will add range hood and a few long open shelves like in the image below (and is also the look i'm going for decor wise)

If study is the primary use, place desk where optimal work arrangement. When I was doing a lot of zoom meetings, I needed to face the door so I could see and communicate with hand signals to the family as they popped by. So for that I would have my back to fireplace. My window faces east so morning sun was a killer with desk under window. What I wouldn’t like is to be tucked into corner, as you currently have, with no view either into house or out window from the desk. But that is me not your husband