If you use an image you did not create, you must provide a citation. Image citations should include the following information at a minimum:
General Format
Reference (No Author)
Title of work [Type of work]. (Year image was created).
Retrieved from URL (address of web site)
Reference (No Author, No Title, No Date)
Many images found on the Web fall under this category.
Try to locate the missing information by clicking on the image,
and/or looking at the bottom of the image.
[Subject and type of work]. Retrieved from URL (address of web site)
Example
As long as you cite it correctly, you can use any image in your presentation.
For other types of creative projects, you'll want to find images that allow fair use (copyright-free, public domain, creative commons licenses, etc. For those types of images, check out these resources:
Creative Commons Search and Resources
Creative Commons is a nonprofit organization that enables the sharing and use of creativity and knowledge through free legal tools. Their search feature helps you look through different sites for images with Creative Commons licenses.
Open Access Photographs & Historical Images
Images from the Library of Congress, now in the public domain.
Historical and contemporary images contributed by participants. Millions of high-resolution images of art, architecture, design, people, historical events, diagrams, maps, and more.
Primarily historical images organized into 18 categories, including Women, Science, Cities, Natural World, Science, and more.
Over 180,000 images that are in the public domain. High-resolution downloads. No permission required... just go forth and reuse!
Primarily historical images organized into 18 categories, including Women, Science, Cities, Natural World, Science, and more.
Websites with Free Images
Over 10,000 images, browseable by category. Lots of clip art and clear photographs. Read each site's conditions carefully.
Search image tags or browse by category.
Stock photography contributed by members. Owned by Getty Images.
Public domain contemporary graphics contributed by users.
Open collection of icons.
Database of icons that can be used for free with attribution.