What does the boy say?

How old is the kid? If he's old enough to express and opinion (and I'm assuming so from the furniture), I'd ask what he thinks. If he doesn't care, then why change anything at all?

Why the question? Seems like a pretty designed room for a boy--considering what most I know wouldn't mind living in. The juvenile sheets are about all I see but they go with the Darth Vader over the desk so I am guessing no matter his age he is committed to all things Star Wars.

I think it looks good as is. Unless your son or you really want to make some changes I'd leave it as is.

Is the large blind green? If so, it doesn't seem to relate to the bedding or anything else so I would consider changing that to white/cream or lined (if you need privacy and more light control) woven roman shades. Is the same thing on the smaller windows? I can't tell from the photos. The upper part of the wall appears to have a different paint color banded around the room. I'd prefer the walls to be one color. The curtains (and pillows of the same color) appear to blend with the main paint color, which I like.

I think it is great as is! Did you design it?

Different desk chair, if he actually uses the desk.

So much depends on what there is about the room that your son doesn't like. If he doesn't like the bedding, change it out. If he doesn't like the paint color change that. What colors does he like?

i have a son who is 32... (now a homeowner, with son of his own) so my advice might be dated.

under 17:

buy a second set of sheets in a solid color that goes with the room, sorta. wash the current ones. appear with both sets in your arms and ask 'which set do you want me to put on the bed?' which ever he nods and grunts at, those are the ones that go on.

over 17:

do nothing. close the door.