When using images, music, poetry or other creative works, it's important to use them appropriately. Generally, including images in presentations or class assignments is acceptable. Selling images or posting them on a website are not. Here are some guidelines from EBSCOhost and definitions that can be useful for understanding copyright.
From EBSCOhost
Copyright of this image is the property of PUBLISHER and the image may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder’s express written permission. The image may be printed for personal, non-commercial use; used in presentations for educational use consistent with the Copyright Act of 1976; but may not be posted on the Web or used in any other form of mass media without express written permission from the copyright holder.
The Full Text of Copyright Act of 1976 is available from: http://www.copyright.gov/title17/
Definitions
Copyright – A form of intellectual property law that protects original works of authorship including literary, dramatic, musical, and artistic works, such as poetry, novels, movies, songs, computer software, and architecture. Copyright does not protect facts, ideas, systems, or methods of operation, although it may protect the way these things are expressed. See Copyright.gov's FAQ's.
“Fair Use” – A doctrine of the U.S. copyright law that allows for limited use of copyrighted material. Four factors should be considered when determining fair use:
It can be difficult to determine fair use. When in doubt, contact the copyright holder for permission or consider using another source.
Public Domain – A work of authorship is in the “public domain” if it is no longer under copyright protection or if it failed to meet the requirements for copyright protection. Works in the public domain may be used freely without the permission of the former copyright owner.