Boys room ~ This gender neutral kids room features bright white walls, Scandinavian inspired decor and custom made wooden beds. The bottom bed even has wheels on it so that it can be moved around when needed.
I would do the boxes next to each other (or shelves for art supplies & books), add a cushion on the boxed (shelf area) with textured pillows. Then add a leg to support the desk on the end with two chairs.
With crappy design, 200 sq ft can feel like a confining trap with little functional value. With great design, like this little room by Moscow& Architecture, 200 sq ft can feel open and perform like a space much larger than its tiny footprint would.