I believe this is now the default for all Explored photo pages. And below all individual photos there is now a message with the option to 'Darken this Photo':

I believe this is now the default for all Explored photo pages. And below all individual photos there is now a message with the option to 'Darken this Photo': "Many websites today are engaging in an awareness campaign about two pieces of pending U.S. anti-piracy legislation -- SOPA (The Stop Online Piracy Act) and PIPA (The Protect IP Act). If you would like to join Internet users around the world in this campaign, you may choose to symbolically darken Flickr photos (yours or others), depleting the web of rich content and letting others know about the potentially harmful impact of these bills. For more information see http://blog.flickr.net/. http://blog.flickr.net/.