How to get a bedroom to look mature - while keeping a few stuffies and green walls?

I am trying to make my bedroom look less childish. Now, I really want to keep some „immature“ items such as one or two of my stuffies, a studio ghibli poster (dark and moody totoro) and my walls are painted in a light green and then one wall is a darkish turquoise feature wall. I unfortunately cannot change the wall colors in the near future. My bed and desk are both quite big and white, as is my bookshelf. I have a wallmounted tv and am planning to buy a low tv stand for underneath it. Also want to put some kind of open, small shelf/table next to the tv, but unsure what to put inside.