Note that plagiarism and copyright are two separate issues. Citing a photo, video or other media file does not mean that you have used the material legally.
Generally using these types of materials:
However, if you intend to
then consider the copyright laws for including photographs, videos, etc. Seek permission and provide appropriate legal notices in the body of your presentation. In some cases, a royalty must be paid in order to use others' creations. In other cases, royalty-free work is available for use under certain conditions.
The photo credit given below is an appropriate one for a Creative Commons image being reproduced on a web site for educational purposes.
(Photo credit: Luke Redmond.Machu Picchu (The Lost City of the Incas).Used under a Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic license.)