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...