The best spot to place a wood CD tower in your room depends on your available space and the size and style of a particular model.
If it would end up being one of the tallest items in your room, you could place your new wood CD tower in a corner in order to avoid an unbalanced look. If it’s a bit shorter than another tall piece of furniture like a bookcase, you could place it fairly close to it in order to create a slender, ascending look.
However, if you’re trying to save space because your room already looks a bit cramped and your wood CD tower isn’t too deep, you might want to consider placing it behind the door.