[wulf]

To be sure, you need the opinion of a suitably qualified lawyer and that will probably cost.

However, I would imagine that a note about the potential problems of having used the images, noting that they were passed on as an example, not as a finished product, should cover you. It would be better if you had something written down from when you passed them on in the first place but am I right in guessing that was an informal "helping out" gesture? Even an email saying "take a look at these and, if they are useful, we can talk about full-scale ones suitable for publication" or something along those lines might be helpful.

Wulf