It’s a lovely bonus room for you, but we need more information to generate ideas/formulate a plan. Please post a to-scale room layout with measurements, including the position of the pendant light fixture. Does that fixture raise/lower? What do you need in the room? A bigger desk? Is the current desk built-in? Do you have a preference on the location of your desk? Do you need access to storage near your desk? Will the free-standing wardrobe cabinet hold hobby supplies or is it filled with other items? What kind of hobby furniture/supplies are needed? Can windows be left bare or do you want privacy? Is there a nice view out the windows?

First thing that stuck out to me was the black colored shades (?)

Yes, Removing them and replacing with curtains or atleast sizing them correctly would look better.

As a first step.