Seems like another commenter beat me to the punch, but to me the obvious answer would seem to be not hosting images at all as they could create a red circle in

Seems like another commenter beat me to the punch, but to me the obvious answer would seem to be not hosting images at all as they could create a red circle in css. Or as others noted reverse the logic so that it shows red icons by default but as long as the services are working then it replaces that with a green icon. And when those external services are down it would go back to a red icon.