I've always thought it has more to do with your own personal beliefs/energy... you arrange things around you in a certain way, and believe it's good for you, so you lend a lot of positive energy/vibes to your surroundings... I honestly believe that if you duct-taped a stuffed giraffe to your ceiling and believed it was good for you, and would bring you health, safety, and success, then your energy would be positive in those surroundings and have the same effect.

That's not to say I think it's a waste of time... if it makes you feel good, doesn't hurt anyone, and gives you clarity, why not?