Functioning Form (an excellent site/blog on interface design) points to an interesting article that covers how designers can be influenced by natural or biological forms. This approach is often called biomimetics. It’s a new science that studies nature’s models for inspiration to solve human problems. He mentions a concept car designed by DaimlerChrysler whose body is inspired by…a boxfish.
If you think about this from an evolutionary context, the way complex organisms look: their shape, color, size, texture, and how they behave: their locomotive patterns; their survival tactics, etc. you’re tapping into an enormous amount of “testing” and filtering of designs for something that simply works well enough to have survived through history.
As a designer, I’m always looking to other work for inspiration and I’m especially attentive to work that has been labored over and evolved over many iterations. Much of the hard work has been done. In nature, we’re surrounded by the latest versions of all sorts of complex systems.
This is all, of course, somewhat theoretical. “Inspiration” can drive design in a very specific way (like the DaimlerChrysler example) or it can simply unlock new ideas and approaches to solving problems. Lord knows staring at a blank Photoshop document rarely helps any.