I've noticed that we don't have a definitive relationship for Flickr URLs. These URLs don't fit any of our existing relationships ("social networking", etc.) so it'd probably be best to carve a special one out.

Example of a Flickr URL: https://www.flickr.com/photos/sportpaleis

I should note this relationship is intended to link to accounts held by an entity (usually an Artist or Place), not individual images of said entity.