The chair would have a sturdy back. The desk would have enough room I could move around easily. My feet would not reach the floor when I sit but neither would getting off the chair be a struggle. I would have a computer, and be in front of a window, but one that sealed airtight, so cold air wouldn't leak in from outside.
The room would have enough floor space that if I wanted to lie down I could. The floor would be comfortable to sit on, likely heated but wood flooring, so I could enjoyable walk barefooted without risking having staples embedded to the floor the way they embed themselves to my current carpet. The walls would be orange, perhaps with my own artwork decorating them.
The desk would be wooden, with a drawer underneath to stash sketchbooks and pens so they don't clutter the place. I'd have a myriad of pens, all different colors and thicknesses. There would always be a pen in easy reach, and my backpack would hang off the back of the chair instead of living on my floor like it does now.
The window would be clear, glass somehow unable to be stained or smudged over time the way real windows do, which would mean I could enjoy watching squirrel acrobatics just as I do now but more easily, without having to tilt my head around to avoid staring at smudged glass instead of scurrying rodents.