It's all smoke and mirrors, of course, typically normal homes transformed from dreary to eerie with just a little effort and imagination. The sole purpose, of course, is to get into the spirit of Halloween, creating an entertaining backdrop for costumed trick-or-treaters, as they make their way along the goodies trail.
Turning the normal into something spooktacular isn't restricted to homes and people, however. With help from image editing software you can even dress up photographs for Halloween. There are various tutorials to be found on the web that will help you turn the normal into the unearthly and sinister. Check out these sites for starters:
Garmahis Photoshop Halloween Tutorials
Create a Realistic Blood Effect Using Photoshop
worldtopdesigners.com Spooky Halloween Photomanipulation