If I put images in the internet, how can I tell your search about them/about the license?
Encouraging use of ccREL embedding like aldenpage mentioned in another response is also in our long-term vision since that would require no additional actions from the creators.
An annual transparency report is probably mandatory with that process, like these ones :
In my mind, the dream is to have the user embed an asset from our servers on their web page (like an updated version of these old CC license buttons [0]), read the referrer headers from the server logs, and then dispatch crawlers that read ccREL [1] data embedded on the page, which would allow us to instantly index content as soon as it is published. Performing broad web crawls searching the web for ccREL data is also possible but probably not what we're looking to do in the near-term.
We have a ways to go before we are able to do this, since there's no easy way for end users to create and embed ccREL at the moment, and there are of course lots of other unanswered questions about how we would moderate incorrect attribution, how these tools might be abused, etc.