Too much white, and too much open space above the guys head.
A nice stripe right above the window should fix that, or you could try adding 'Paintings' and wall decorations lower down, and just avoid showing the very top of the wall. That way, you don't have too many stripes running around all over the place, and you could have a bit more unique look.
I like the tiny red stripe between the grey and white, and you did well on the computer desk. It looks like you put a grey stripe right down the middle of the couch, even though it's probably best to leave things like that one color.
The book shelf would look more natural if you took several books out, and then twisted one or two to face the camera. You could also raise the supports one plate for each shelf, take out some books, and then have the rest leaning over with a bit of headroom. Because everything is nice and lined up, it looks like a multi-colored modern art thing as opposed to a bookshelf. You should also consider stacking something on top of the bookshelf, nothing big, but just a little something.
The bookshelf and the open, blank headroom are the two biggest issues, but they shouldn't be that hard to fix.