The University’s copyright license covers both image and YouTube use in class/ppt slides/eLearning site (under some conditions – e.g. providing a copyright notice).
For image use you will find more comprehensive details available on the copyright website at the following URL: https://library.sydney.edu.au/help/copyright/artistic-works.html. You will find notes on recording or posting on eLearning site here as well.
Regarding YouTube material; linking and/or streaming to the class is allowed. It is recommended that you link to a webpage or website rather than reproducing or downloading it, as there are no copyright restrictions on linking to websites.