What are the dimensions of your desk? Do you need to be concerned about your background for video conferencing?

I'd add some curtains, a more comfortable desk chair, a rug and a chest of drawers that matches your desk. A comfortable chair could go where your bookcase is now, and the bookcase in the corner to the right of the window. The room would look less like a bedroom if the closet door and its trim were painted the same colour as the wall, instead of white.

First, I'd pick up a rug, curtains and fiber shades. Rug should cover all of the floor except 12-15" around the outside. Curtains should hang high and wide (to the ceiling and barely covering the window frames.) These items will add life and warmth to the office, and make you feel comfortable working there daily (especially if you pick items in your own happy color favorites.) I would go for a comfortable pair of upholstered armchairs instead of what you propose. Instead of the leaning bookshelf, which looks too collegiate, I would get a low bookcase to set on that wall under the light switch. Hang a big piece of art you love to look at 5" above it. If you do video conferencing, I would turn the desk so you are sitting behind it and facing the closet. Hang more art (or your professional credentials) there. You may want to do some practice Zoom conferences to see how you look with the gray wall. It is not really flattering to most skin tones and may make you look washed out. There are lots of tutorials online about how to present yourself in your best light for these electronic meetings. Paint may be in order, even if you don't do conferences, because I bet your favorite happy colors don't include gray!

tons of ways to spruce it up. color, rugs, lighting. I'd add some type of book case. Look at Ikea bill bookcase hack for office. you could do something like this (your window would be in the middle. or choose another wall.

I love this room w/the bright white built in's (Ikea!) the sconces, the navy blue walls w/bright white trim and desk.

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this is a good idea if you need some extra storage or visual calendars.

I'd want light and bright and cheery.

You can always do some sort of book case on either side of the window

Check on craigslist for an old wood desk. give a good cleaning and sanding, prime it and paint it!

bring in some colorful drapes, and other accessories

I think this desk can be done w/ikea products

Get a butcher block and use the Ikea cabinets to mount it

What is the closet used for? Is it full? I ask because the room is small and perhaps adding a shelf/surface in the closet to house printers, fax, file would be a good idea. The desk has straight lines and could really lend itself to a transitional, and more modern esthetic. Do you like the wall color? Studies have proven that individuals don't work well when their back is to an entrance. So although I can see how you likely have your desk positioned to look out the window I would actually change it so that the back is to the closet and you can look to the left out the window or to the right and see the doorway. Depending on what is in that closet the door size is large and will limit furniture layout. I would really look into removing them and as I said before doing some type of built in shelving and lower cabinets/drawers in the space. something like this

Ikea Besta is great for storage as well. I have used them in a few spaces ive done and they look sharp when mounted off the floor . Here is one in an office we did.

Before anymore suggestions can be made it would be helpful to know what the answers to the questions that have been asked are as well as the colors you're partial to. Then we can make more specific suggestions, do a floor plan and give you some ideas.

I would Not do any built ins or bookshelves...to me it’s way to busy look. Keep it modern., fresh and clean look. Add warmth with a rug, curtains, plant. Get a different White desk with more drawers and storage space, do something interesting on the wall, maybe a futon. don’t overwhelm it with furniture and stuff.