A small business might get away with misappropriating a piece of artwork for commercial purposes. But Apple? Yeah, that's probably going to get noticed -- especially if it were to use such an image in a keynote for the latest Macbook Pro and then prominently display it in related advertising.
The image in question, called "Eye Closeup" (above) was created by one Sabine Liewald. Based in Switzerland, Liewald is claiming that Apple did not appropriately licence the photo for use in advertising. The company did however get the proper permissions for "'comping' (or layout) purposes only", according to Patently Apple.
Obviously, if Apple has used the photo without correctly licencing it, Liewald is entitled to whatever damages she is owed. That said, I doubt Apple's intent was malicious; it's entirely possible someone in Apple's marketing department had a brain fade and accidentally slipped the image into "OK to use" folder. It's unlikely Apple would skimp on the necessary payment either.
If you're wondering whether Apple is taking the claim seriously, all one has to do is browse over to the "Design and layout" section for the retina Macbook Pro on the Apple website, where you'll see a very different eye image.