Cool Shower Curtain
If you have some theme going on with the Halloween decoration around the house, you can include bathroom decor with it as well and cool shower curtain can help you a lot to keep the theme intact.
With the cool shower curtains you can go in many directions with the theme from fun to horror or to prank someone. If you are looking to go in a horror direction you can use bloody shower curtains. Or you can buy and hang color changing shower curtains with the color changing mat. They can change to the color of blood or some other fun color if you are not doing horror decorations.
Alone cool shower curtains will not be as fun as bath sets with rugs and shower curtains will be. It will make the theme look uniform and more fun and exciting rather than only hanging a curtain. These curtain set can also be in the form of some fun cartoon characters or just some funky design depending on the theme you are going for all around the house.