Do you have to add art? It is a small room and the wall paper is heavily patterned.

The wallpaper is so dark that I recommend that you make sure the wall art is very light in color. Art.com has a wide selection of art. Get a print, then get it framed in plexiglass where you live. Below is just one example. Another suggestion I'll make is to add a carefully placed wall mirror (make sure there is a good reflection of the window - put it on the right wall that we see in this picture) to get more light in the room. Additionally, please educate yourself about lighting and get good and appropriate lighting. Lighing is often seen as an afterthought. However, in this dark room, it will be crucial to attend to it. https://www.art.com/products/p58484854494-sa-i12655342/paul-cezanne-trees-and-rocks-no-1-c-1895-w-c-graphite-on-off-white-laid-paper.htm?upi=Q1W5EE92H1VXB&PODConfigID=9436046

Any chance you could be convinced to do a long closed storage credenza on the wall with the shelves? It will allow you to lean a large piece of art and do a table lamp.

Or maybe you have a tall dresser that could work - you want something to serve as a spot to lean a larger scaled framed piece of art and then layer with a lamp, etc. I’m suggesting closed storage so your eye doesn’t see so many things competing with the walls. This isn’t quite right but just a quick mock up:

Pottery Barn's Pacific line is on sale and the 'fog' finish might be nice with your rug, etc. You could do the long writing desk and then maybe 2 of the file cabinets to act as a credenza/art leaning spot. I'm just having a hard time with the white desk and bookshelves (both of those finishes seem like an outlier with your walls and all of the open shelving creates visual competition with your beautiful walls). Also struggling with the fact that I wouldn't want to put art up on the wallpapered part of the wall. The art leaning method works well for your situation - but then, it needs a spot to lean lol...the domino effect of design decisions. Good luck! https://www.potterybarn.com/products/pacific-desk-with-drawers/

You could go simple, so as not to detract from the wallpaper and look to complement its design.

You could make the room feel more interesting/eclectic. Either way, I’d either move the bookshelf to another wall as it feels awkward there…or replace. Room overall will feel better balanced.

Why not visit a local art gallery and buy something inexpensive from a local artist like a simple woodblock print or etching? Maybe a black and white print. Original art isn't always expensive and can even be found in thift and antique shops. Love the wainscoting

Maureen I wish I could mock up like you! But I do think that the open shelves and gallery wall does compete. I still think closed storage, one larger statement art piece and a good sized lamp will look and feel elegant.