[pessimizer]

Wouldn't the problem lie entirely within some publication serving an image that they didn't have the right to sublicense, through a protocol explicitly meant to be shared on other people's websites?

Like the "media company" said, I think you should make a claim against the site you linked to. Their redistribution of the image through a protocol meant to show up embedded on other people's sites is an implicit claim that they have the right to sublicense the image.

edit: the claim would be a favor. Just ask them for what you paid, and charge them for your time. They'll pay you with petty cash and get their lawyer to come up with an image policy to avoid difficulties in future.

Anyway, websites don't like hearing that people can get sued for linking to them.