It is important to be aware of the laws governing image rights. If you are using images in your art work that are not original, you need to respect other creators' content and the rules about using them. Here are some resources that may help you figure out whether you can use an image or not:
Visual Resources Association Intellectual Property Rights (IPR) and Copyright
The Visual Resources Association has produced several sets of guidelines and tools related to images and copyright.
Digital Millennium Copyright Act
Comprehensive database of art images to view, analyze, download, or save for use in presentations. To save images you must set up a personal account with JSTOR.
Millions of primary source documents from across the world spanning the 15th - 21st centuries.
You may have seen on Flickr or elsewhere, captions that say that an image is protected by the Creative Commons license. Creative Commons is a type of copyright or licensing agreement between the creator of an image and everybody else on the Internet. If you look closely, the Creative Commons license that goes with an image will tell you exactly what you can and can't do with an image. There are four basic qualifications:
These four factors can be combined in various ways. You can look at the official website of the Creative Commons to find out more about this.