Depending on the facts of the situation and local law, a number of parties could be held legally responsible for unlicensed image use.In nearly all cases, however, the end user of an unlicensed photo bears the ultimate responsibility. Additional circumstances you may not consider: a third-party web designer supplied the photograph, or the photo came as a part of a web template. Regardless, it is the end user's responsibility.
Just as you verify day-to-day records in your organization, you also have an obligation to verify that you have a license to publish all content on your website. A license fee is still owed even if the picture was removed and there was no direct, quantifiable economic gain: a commercial gain is often indirect.