I love this sculpture by Teresita Fernández. It's made of laser-cut steel, painted green on the back side and mounted a few inches off the wall. The pattern looks like shadows and light below a tree. I didn't realize it at the time, but the artist also created Seattle Cloud Cover at the Olympic Sculpture Park.
Depending on where you focus your eyes (or camera!), the sculpture looks completely different. Here I've focused on the sculpture itself.