I've been wondering how Aviate identify and curate their lovely background images. They all come from Flickr... but not sure what groups they'd be following, o

I've been wondering how Aviate identify and curate their lovely background images. They all come from Flickr... but not sure what groups they'd be following, or search parameters they'd be using to narrow it down. Prior to this change... I presume they would be restricted to CC-attribution?