@Shani I'm wondering what that black over white object near your desk is. I'm also wondering what you like about the room and what you don't like. It sounds like what you don't like is that it is lacking color. Personally, I would develop a whole-house color scheme to reduce mistakes like having a completely colorless home: https://www.fromhousetohome.com/whole-house-color-scheme/ Would you like your room to be a mix of blues and greens? Or is there a different color scheme you like?

I looked up "chic office chair" and wonder why "office chairs" have to have wheels. I hate wheels. The stupid chair sometimes moves out of the way when I try to sit on it. But maybe you aren't as clumsy as I am. I saw a couple pretty ones that would coordinate with the only colorful thing in the room but I don't know what your favorite colors are. You don't want a huge chair in this room so I wondered what you think of the style of this one: https://www.roveconcepts.com/mia-office-chair Remember, you can always use a regular chair as a desk chair. You can find a used one and paint it a favorite color if you want. Or put a colored cushion on it.
​The curtains and new light fixture... Are they yours or your landlord's? Is the light fixture a lamp you can take with you? https://www.homedepot.com/p/Zompoo-Modern-63-in-1-Light-Dark-Blue-LED-Dome-Reflecting-Standard-Floor-Lamp-for-Living-Room-with-Metal-Shade-and-Foot-Switch-ZP-HL3095-PB/339662401 Do you want to look out the window? Or would you like to shut out the light so it does glare on your monitors? If you can't paint your walls, but want color, try sheers, even where there aren't windows (but don't block the doors with sheers): https://www.bedbathandbeyond.com/c/window-treatments/curtains?t=28420 Personally, I would develop a whole-house color scheme to reduce mistakes like having a completely colorless home: https://www.fromhousetohome.com/whole-house-color-scheme/ Would you like your room to be a mix of blues and greens? That's why I suggested what I did. I did not suggest an area rug, because I think it would clutter your room unnecessarily... you can add color other ways. And a nice field of warm wood would balance the suggested blues and greens. But maybe you like other colors.

I would flip the desk around so your back is to a wall. One larger cabinet would hold all the things the assortment of small bookshelves you have and make the rooms feel less cluttered. Why a rug? Chairs work better when not on a rug. For configuration help we need measurements of the room, doors windows included and the furniture. Your owner will be ok with swapping the light fixture but not let you paint??? We have never had an owner turn down a painting request. We did the painting. Some have paid for the paint some have not.

I'd swap the green piece for the desk and hang the art on the door above the monitors.

Look for a black patterned area rug, let the green be the statement color in the room.

https://www.amazon.com/BERYTH-Adjustable-Leather-Computer-Armless/dp/B0CPHVT1YB/ref=sr_1_8?crid=S41IIHWHV35N&dib=eyJ2IjoiMSJ9.ENrIKIw9QDOVjLwpkwace_b0Q_g1E90MH50GBkHRQJCpNzMjlPHHouWZLKzNmsszCGz6D5RL0I-UcyIgzXvjY5gDO6Xv5iEeivN3gAAjb914ZCJvAXQis6sVm69r4d7LXb_X9cuechs0U-r-t-bkCGQ8lGzG_9PTUwvGT-YDwxXbVHMNwApzoFRpW2iMdKiHNAVI8YHevOWwjtoNLtd8ILFuPDwL9qZ39F8BLHHp6DNuluypLkuWYrn4IozFQP7jmGl31OCi_i3DBzcfTaEbrkyWFGI4zbXU3LHdLCzTjJs.3zN7Ei6TnWJzEbm5FRdT-0VwSnDQmTeH8TEtvvQhJm4&dib_tag=se&keywords=modern%2Bdesk%2Bchair&qid=1779045999&sprefix=modern%2Bdesk%2Bchair%2Caps%2C166&sr=8-8&th=1 .

https://www.amazon.com/Washable-6x6-Square-Rug-Resistant/dp/B0GS2RHNFZ/ref=sr_1_4_sspa?dib=eyJ2IjoiMSJ9.5M6i-QPsinG6sm3T3WpTO9Egu7w-XI5jUB46AgfIy8sN16GaIlUEVQLOFAeoLYu57Zn-qrUYsZ1WTk1AyxVCp_hxIZiYOlucJLVjq0prMgrL9VjdkHzSllpR0kveMieLZJ6zMKjl7S1WkUfAqOpt_PLrKrlAAjASa8ktNEPVq8vV9-w7K-JNRwM42uEGcUxW2d1Ocv7m_j1q_enf2hg_MzFIiqr1DyRHq6K6By9YTc9-5BmtBCbMnIlcB-mOlrYIi0J8sr1uao6JRdjI8riCjSdwykzEtw-NPR2ASahgRdQ.oQXX_UbPaLe7YTo3iR4Md5HTowmWIMpF-cptzs4kM1Y&dib_tag=se&hvadid=778079217816&hvdev=c&hvexpln=67&hvlocphy=9008497&hvnetw=g&hvocijid=11418768535357537854--&hvqmt=e&hvrand=11418768535357537854&hvtargid=kwd-462141537514&hydadcr=15827_13843840&keywords=6x6%2Bblack%2Barea%2Brug&mcid=9cfb9946c1a83958a208bd7c26382adb&qid=1779046346&sr=8-4-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

The cabinet is pretty and adds some color to the room. I would, however, consolidate the smaller bookcases into one taller bookcase placed on the short wall by the entrance door to save floor space. I would find something with a combination of doors and shelves to hide the water and paper towels/toilet tissue that you are storing in the room. Then move your desk to the longer wall as suggested. Move the decorative cabinet next to the window where the desk is now. Trade the mini blind for a pretty wood or lined bamboo blind for texture. Add more interest with some more artwork and find a pretty office chair that doesn't read "office".

Adding in wood in the bookshelf will warm up all the white walls.

This is only $159.

A rug will just get in the way of moving the chair when needed.

If you want to add some greenery, tuck a fake plant into the corner.

I have a study in my house - and my desk chair doesn't have wheels/casters. I have an area rug in the room + little plastic things that stick onto the underside of the chair legs (= you can't see them). The legs glide across the carpet easy enough for getting in and out of the chair. I didn't want a typical office desk chair - and when I purchased the furniture for the room, they didn't have any nice/chic style desk chairs with wheels that I liked.

However, I have now seen quite a few people use chairs like this for an office chair -

Below is one from PB (different fabrics are on sale + PB has other desk chairs, with styles similar to the one below, that are also on sale):

The one below is from Overstock - just in case you'd rather have something with stripes/pattern vs. a solid color (has different color patterns):

What's nice about the above type chairs (in addition to having hidden casters) is that they look like accent chairs = you can use them for an extra seat in your living room when needed.