The design principle that inspires me is spatial depth. Here are some designs where spatial depth is used
from http://abduzeedo.com/beautiful-artworks-evgeny-kiselev
from http://rhiannondoherty.blogspot.com/2008/09/fundamentals-of-design-week-4.html
from http://kevinsartwork.deviantart.com/art/FND112-The-Fundamentals-of-Design-314677296
