I wouldn't add too much to the scenery ... there's that empty wall, yes, but there's already a very big picture or tapestry across from the desk covering almost the whole wall, so, see that you don't interfere with that special pattern and color ...
I'd say, as the next room with lots of books and a board game as well as the rest room suggest having more people or guests over there every now and then, I'd add sth like a sideboard or a small cupboard with or without drawers to the empty space with some mugs or glasses and a water jug and/or one or a few 'D'ni Lake' bottles and maybe a simple bowl with or without some fruits and/or a plate with bread and/or cookies ... you see, sth like this ... You could also just use one of those shelves, which you already have in the next room and fill this up a bit with what ever to make being there look and feel comfortable and inviting or hospitable ... you can place a big vase (like in Fehnir's House e.g.) or some bottles next to that sideboard or maybe you add just a big vase and/or another bookshelf and a picture ...
In your journal you say that you liked to hang out and relax in the Camp Bravo nighttime version, so, you could add a picture of that ... In Shinelight Manor you have many beautiful pictures hanging or what about a picture of that fire marble apparatus ... Yeah, I believe that is it for now from me ... Take your time and see what feels/looks right for you, Justin ...