i would say, choose a theme just for that space and work around it! for example: maybe "asian" theme! paint the back wall RED or ORANGE, have a piece of buddha statue on the top most rack, you can use one shelve to just hold books with some decorative book ends, and instead of the chair, you can use the asian trunck boxes (if you google for asian trunks, you can see what i am talking about! - look for square boxes), this way, you can also tuck those boxes under the desk/shelf when not in use and the trunk could also be a storage for your files - you can also place a floor vase with some bamboo sticks - the asian theme would really work here as your wood is black/brown this would also turn out to be a peaceful writing space - enjoy!

Not really sure what you're asking. Interior door? Exterior door? Every door is made from different materials. Solid core is different than hollow core. Some are fiberglass. But your basic water based paint works on most doors. Doors are usually painted in a semi-gloss finish as is trim.

You may also want to consider a screen or pass-through bookcase to visually divide the "bedroom" area from the living area. I like your table and platform bed ideas. Consider whether the radiator will have enough room to "radiate" with a bed against it though. www.twitter.com/216Sharon

the 9' ceiling height will definitely help you with this. Here's what I would suggest (not knowing how far the side window is from the wall with the door on it: Use the wall with the door as the bed and closet/storage area. Build a closet, and put a loft bed at the top. Because it would have to be custom built, you can decide how high it is or how much storage you need. Kind of like this: [houzz=] or this: [houzz=] Can the space below the back window become a desk? And or/build a desk there with storage flanking it. Keep in mind that this isn't a very large room, and he'll probably want as much floor space as possible (at least my 8 year old does!).