Some people over obsess on certain thing. Some things can be alright to obsess over while others its just way out of line and isn't appropriate. These things can range from a sport to people, it all depends on the person.
It's always nice to have pictures up on your walls of friends and family or even a famous person's poster. However, some people have their whole room decorated in one theme. This could be a person who is your idol, a sports team, a specific sport, just by color, flowers, etc. Whatever you want done to your room, make sure you like it because I bet your parents don't want to have to change your room every year. When you're younger it's usually decorated by your parents by like clowns, or some character on a TV show. However, as you get older, you learn that it's better just to have a plain color in your room and just add some items different items to it. Well if you're a volleyball player and not too old, you may want to have volleyball bedroom apparel. You may buy these items, but it may just as fun to put a twist on it yourself.
Some things you could do to go with the volleyball bedroom apparel is to hang up different things on your walls. For example, you can hang up a volleyball jersey or even volleyball team socks. Also, you could hang up some pictures of volleyballs to go with the theme. Whatever accessories you pick, everyone will know that you're a volleyball player at heart!