It's a simple overlay of a blank 1x1-pixel GIF, with class "img_hidder," so this rule should let you save all those salacious pix:
This thing isn't an ad, or an anti-adblock measure, or malware, or a social-networking annoyance, so don't count on its appearance in a mainstream list and just add the custom filter.
There's a buzzin' in my brain I really can't explain; I think about it before they make me go to bed.