I love any house decoration that messes with reality in a way. On the smaller scale, that can mean having lots of mirrors to make the space look bigger. On the bigger scale, that can mean making the furniture on one side of the room smaller so that people think they are growing when they walk across your house. When it comes to home decorating, I'm of the Willy Wonka ilk.
What a way to make your house guests feel like they're tripping on acid. "Jane... did you put anything weird in that lasagna? I'm starting to see the walls bend." These are very cool, but I'd avoid putting sentimental family photos in them. No one wants to see grandma's face bend into a hard edge. Especially if it's your only vintage copy of the photo.