Avoid Gaudy Shower Curtians
This is an easy trap to fall into. Say, you saw a shower curtain you liked online. It has the shadow of the person holding the knife from the movie "Psycho." You've never seen it, but you think it'd be cool to hang that in your bathroom to show your visitors that you're a cinephile. Little do you know, you're actually just showing them that you don't know how to design a bathroom...
Don't Do It, Just Keep The Curtains Simple
If you just get normal shower curtains that match the same color scheme of your bathroom, then you'll look like the adult that you're pretending to be. You don't need that themed shower curtain. It will make you look like you still have the design sensibilities of a college freshman.