$20 for 25 images? What's that saying about a fool and their money?
I wouldn't worry too much about having a photo on your iPod, so long as you're not charging people to view it. It's different than music and movies, in that the way you copyright an image is mostly different.
This would be no different than downloading an image and using it as your background image, it's fair use. Put it in a book, and sell it, you're asking to be sued.
Besides, no one is going to stand around the airport scaning peoples iPod's for stolen images or even music. There would no way to prove you didn't obtain the owners permission without contacting each individual images owner and asking. That would be impossible.
Also, as Lurk said, those images were likely compiled from other collections, and I doubt they obtained the owner's permission. Hence the note on the bottom of the page. In no way would you be protected, since buying stolen goods is still against the law.