I know this is an old thread, but I just had a similar situation.
I designed the client's site about 5 years ago. He supplied all of the photos to me and claimed that he had paid Getty for them. A few months ago Getty contacted him and said that he was using their photos illegally.
The client tried to push the responsibility off on me and asked me if I could provide him with the info that showed that he/we had the right to use the images. I reminded him (and it was clearly spelled out in my contract) that he provided the images and that the assumption was that he had obtained them legally.
So he had to deal with Getty, and even though we removed the images he still had to pay for their prior use. So it cost him about $5000 in the long run.
The client was a jerk anyway, so I was secretly glad that he got caught after what he put me through during our design process.
-Jesse