All product images must meet Amazon.com general image standards as well as any applicable category-specific image guidelines.
So, beware of your category rules! With that said though, generally speaking, here is what your image needs to include for it to be copyrighted.
© 2013 Name Of Company. All Rights Reserved.
You don’t have to put “All Rights Reserved” on there, but you might as well. The symbol, then the year, then the name of whatever person or entity owns the copyright.
That’s enough for common law, which generally lets you tell other people to stop using your stuff, but doesn’t let you sue anyone for damages. For that full protection, just go to the Library of Congress site and actually FILE your copyright. You can do that online for $35, while a paper filing costs $65. Instructions and more are located here, http://www.copyright.gov/eco/
Here is the best “general” guide to images we have seen to date and the one we reference when we are creating images for ourselves or our clients, Amazon Photo Guidelines.