1. Look for public domain or images for which explicit permission for reuse is given (e.g.,
Wikimedia Commons
Flickr Commons
Free-Images.com
https://www.google.com/advanced_image_search with usage right set to Creative Commons licenses
2. If an image is from an institution or publisher, look for a policy.
3. Contact the copyright holder and ask for permission to use the image.
Images from MU Archives and Special Collections may be used in student projects without seeking permission, as long as any "C number" in the original image caption is included in your image caption.
Images of all sorts--photographs, prints, paintings, illustrations, diagrams, graphs, maps, film, videos, digital or not--are protected by copyright just as other materials are.
Music that is fixed in a tangible form--sheet music, scores, written notes, any sort of recording, whether analog or digital--is protected by copyright just as other materials are.
If the material you want to use is not in the public domain or available from a licensed resource, conduct a fair use analysis to see if your proposed use would require permission.
NOTE: If you are dealing with photos or video of people, you may also need to consider privacy rights. The University requires written consent from anyone included in an image.
Complicating factors: