Most images on the Web are copyrighted, even if they don't say so. Only the copyright holder can grant permission to use an image.

In some cases the use of an image may be covered by Fair Use, especially for educational purposes. 

To avoid copyright infringement, look for images that are in the Public Domain or have a Creative Commons license that allows for reuse. 

Remember to cite and attribute all images both internally and in your Works Cited or References page. 

If YOU are the creator, illustrator, or photographer of your image, you own the copyright and do not need to cite yourself.