Meet my new best friend, the stencil. This is perfect for a bathroom, or you can just keep it to one wall.
The company, OMG Stencils has a wide array to choose from ranging in the $20's-$40's.
This patterned paint roller works just as well, maybe even better. This way if you have a little mess up, it will be barely noticeable. This Etsy find is from a company, Not Wallpaper with rollers ranging from $20-$40.
Now, I just have to find the right color and pattern.