Are you willing to paint the furniture black? if yes do so ,now let me see what I can think of ,your son like music I see so lets work with it .

to start we need new bedding

Here are some ideas. Pick out four or five new bedding options from overstock.com or Target or your favorite store. Send him the links to choose one. No dust ruffle, he has storage under his bed., I can see from the photos. Get plain sheets, not patterned, to go with the new comforter and shams. Replace his bed pillows. Pick up a paint color from the bedding. Use paint, not wallpaper. Roman shades can be custom made from panel curtains that coordinate with the bedding, or just use the panel curtains as is.

Get the carpet cleaned professionally if it is still good. If not, pick a medium-low pile plush carpet with a good pad. Berber has been out of fashion in a lot of places for some years now.

Buy some all-one-color plastic hangers for his closet and enough wooden hangers for his jackets and coats. Remove all wire hangers.

As for the stuff, you can roll up the posters in a tube, pack away ALL the things on top of the dressers, and put all the boxes in the closet. The desk area full of computers is something you can photograph, send him the photos, and ask which computer parts he wants to keep. If he says "all", he can sort it out himself over the winter break. My guess is that he is using a laptop at college and all of his computers at home are obsolete... but ask him to deal with it.

Leave all the old artwork off the walls. He can go through it when he returns to decide what he wants up in his room.

Sorting through which chairs he wants to keep can be done over winter break. A luggage rack is a good idea for guests.

I love the paint color and bedding that Genevieve suggests, but find the art still somewhat juvenile. With the suggested backdrop being so neutral, you can use his favorite color in carpet and artwork...something Ellsworth Kelly inspired.

dclostboy's choice just made a leap of 20 years in maturity level for the artwork.

Wanted to show color rather than black and white, but didn't want to violate copyright :)

@dclostboy: may I ask how you chose your screen name?

In going with your original idea of navy, I'd suggest the following. Roller Blinds for the windows with bold paisley drapes:

Removing the desk, chair and one of the dressers. I'd replace the desk with a lighter, modern glass writing desk and pair it with a soft comfy chair like these:

Since the space is on the smaller side I would advise keeping the walls a neutral but warm light color. I like BM Barren Plain for this room:

Now for the bed….you are working with a captains bed which can seem juvenile. I feel a good way to counterbalance this would be using simple bedding such as white or off-white and layering in menswear inspired accessories in navy or grey. I'm envisioning woolen pinstripes, houndstooth, tweed or plaids. These beds aren't exactly what I had in mind but they portray a similar idea:

@applepie, I could say something cool like Kiefer Sutherland and vampires, but really a Peter Pan reference from many years ago that stuck.

@dclostboy: The Lost Boys, I thought so.

Now back to the poster's dilemma.