Rosalind - 2:42 pm on Jul 21, 2013 (gmt 0)
I surf with the referrer blocked. It makes logging in or completing some forms difficult, although I don't believe it affects images on many sites. So humans with blank referrers are going to be used to a small amount of inconvenience.
One solution may be to redirect the image to a message that says, "you're seeing this because your referrer is switched off". If you want to go further, put up a link that leads to a cookie which will make the images visible again. If it's one click, it might work. Just don't ask people to re-engage their referrer, as Pinterest does, because that's too much hassle and may not be possible for some users.