Forum Brand Bloody Bathroom Sticker is an easy way to add a zombie vibe to your Halloween decor. The sticker has a zombie face with hands pressed up against the glass.
The application is easy, a simple "peel and stick" design which is also easy to remove.
 
While this was designed with a bathroom mirror in mind, this can be stuck onto any smooth, non porous surface, so can also be used as a spooky sticker on windows or glass doors.  Simple but very effective!