From a CC Blog Post by Jane Park:
Today CC Search comes out of beta, with over 300 million images indexed from multiple collections, a major redesign, and faster, more relevant search. It’s the result of a huge amount of work from the engineering team at Creative Commons and our community of volunteer developers.
CC Search searches images across 19 collections pulled from open APIs and the Common Crawldataset, including cultural works from museums (the Metropolitan Museum of Art, Cleveland Museum of Art), graphic designs and art works (Behance, DeviantArt), photos from Flickr, and an initial set of CC0 3D designs from Thingiverse.
We will continue to grow the number of images in our catalog, prioritizing key image collections such as Europeana and Wikimedia Commons. We also plan to index additional types of CC-licensed works, such as open textbooks and audio, later this year. While our ultimate goal remains the same (to provide access to all 1.4 billion works in the commons), we are initially focused on images that creators desire to reuse in meaningful ways, learning about how these images are reused in the wild, and incorporating that learning back into CC Search.