A pre-teen is ready to learn to hang up or fold his clothes, straighten his bed, and part with childhood toys (or most of them). Sometimes you just have to wait until they get tired of their own messes. Next sheet-changing day, have him strip his bed and show him how to put the sheet on. Ask him to put aside five things he can donate so another child can enjoy them. Put them in a bag in the trunk of your car until you have 15 things to donate. He may also change his mind and he will be relieved you still have a few of them. Kids books are something he may be ready to donate.

Not far off with the medium blue, and natural / blonde color -- the other room is sedate? neutral paint, and darker furniture.... ? the curtains could be a change, and bedding.

Exotic masculine direction? if he likes adding tan to natural furniture color - I think it could be 'cohesive' as they say.

If keeping bookcase to the right of window it can go. Or bookcase elsewhere. You can move bed to bookcase wall. or wall across from it.

Some ideas: try moving the bed where the dresser is, replacing the curtains with a matchstick shade to unify the pale wood and make contrast against the paint color, things could be stored in some light wood colored (to match furniture) baskets. Shelves could be painted the same as the wall paint to "disappear." Baskets would give contrast in those shelves. Another idea: a black high gloss paint on all furniture to look like a set or navy blue.

If your son is reluctant to get rid of his personal things, don't force the issue and make change unpleasant loss. Instead, either invest in some relatively inexpensive plastic storage containers or just pick up some square milk boxes from the local grocery store and a sharpie to number and label them and see what he might be ready to store. If next year he hasn't wanted anything from the stored items for a year or more, he might be a lot more willing to part with them either as donated items (especially during the holiday season of gift giving) or at a yard sale if he gets the proceeds to open his own savings account and/or purchase something else he wants.

Consider defining the two spaces differently:

One would be his bedroom with his bed and chest of drawers for his clothes and shoes. A couple of clear plastic under bed storage containers could be a good investment to store items your son will want to keep in his bedroom such as shoes so as to not put their smell/dirt in his closet.

Define the other room as his studio where he engages in whatever activities he enjoys.

Decorate the two rooms accordingly.

Unless you need the second bed for a guest bed, you could put the mattress and foundation of the second bed on the bedroom bed (raising the height of that bed) enabling you to dismantle and store the headboard and foot board of the second bedroom (unless it is a twin that could be made into a "day bed" for seating. That create more space in the office/studio for whatever storage items you might need to ensure everything can be put away ... even if it's only in stacked plastic storage containers.

Decorate the bedroom in a conservative -- more adult -- way with solid color bedspread and matching pair of pillow shams on the bedroom bed; and, if possible, use the chest of drawers and furnishings that match the bed in the room for clothes storage. Hang the diplomas in a row over his headboard. Put the headboard of the bed against a solid wall and put a lamp on a bedside cabinet or table with an alarm clock beside it.

Put everything else in his studio and have your son find a way to put everything away except for what will appropriately/logically fit on the open blue bookshelf. Will all the stuffed animals fit on the top shelf? Do you have a deep (analog) tv cabinet that could be repurposed for storage of large items -- even large pieces of poster paper?

Now comes the decision the two of you will need to make together. Do you put his desk in his bedroom for him to do his homework there, away from distractions, or do you decide that the studio is an office/studio and put his desk in there?

What does he like about his room and want to keep the same? What does he dislike? Has he expressed a desire for something different -any activities that his room does not support at present?

Will both rooms be his or just one?

How old is he?

In either room, center the bed on the longest wall. In the blue room flank it with the two bookcases. If he takes the other room, flank the desk with the two bookcases facing each other. The blond table with drawers might be good in your pantry or elsewhere. In either room you may be able to fit the short blond chest under the window or in the closet (which you can reconfigure for more hanging space.) I see a lot of table games in the bookcases. Does he play those in his room or can they be moved to a family area? Try getting a plastic tub for all but his favorite couple of stuffed friends. Replace curtains with shades and see if he'd like some new, more grown-up posters. Paint the bookcases in his favorite color or try black if he doesn't care.

Center headboard of bed on longest wall. One bookcase on either side of bed. Dresser on opposite wall. Then see where the desk will fit. Get rid of the young child blue walls and paint with something he likes and will be more appropriate in a couple of years. Medium grey walls and blue accents are an idea. Storage can be in the adjacent room.