Google Images is a great tool to see the work of many photographers. For your presentations, however, the images may not be high enough resolution to project well. It's possible to find useful images with introductory information, and you can even use the advanced settings to limit to works that are in the public domain

Limiting by Usage

The image below shows how you can use the built in Tools option in Google Images to limit to Creative Commons images. 

(click on image to enlarge)

Flickr's The Commons

"The key goals of The Commons on Flickr are to firstly show you hidden treasures in the world's public photography archives, and secondly to show how your input and knowledge can help make these collections even richer."

(click on image to enlarge)

Wikimedia Commons contains, according to the site, "a collection of 58,396,226 freely usable media files to which anyone can contribute."Files include images, audio, video, animations, maps, and other multimedia. Users can choose from multiple images sizes when downloading, and each image is often accompanied by information about the work depicted as well as copyright information.

Image Source: "PNG logo with text" by Wikimedia Foundation is licensed under CC BY-SA 3.0

Searching for Creative Commons Licensed Images

(click on image to enlarge)

If you're searching for an image to republish (on a poster or in a paper, for example), you'll need to make sure you have the right to do so. Copyright holders can use a Creative Commons license to assign usage rules and let users like you know what can and can't be done with images. Use the Openverse (formerly Creative Commons CC) Search page to find licensed images that you can use for scholarly purposes.

• As shown in the image below, there are easy to use filters that allow you more control over the types of licensed images you can search. You can also search Openverse for audio files.

(click on image to enlarge)

Websites for locating some subject-specific images