Pixolu is a new way to search pictures based on relevancy.  It can find pictures based on appearance, and help you find say a picture of pumpkins, but pumpkins in a patch, but no pumpkin pie, or carved pumpkins. similarity to each other.

Basically the pictures load based on a keyword, so then you simply select the pictures which best matched the result.  Pixolu then tries it’s best to further match the results to better fit what you were searching for.  In the end you should have exactly what you want… hopefully.

http://www.pixolu.de/