Can an image found on Google be used?
The fact of finding an image, a video or a text on the Internet does not mean that this material can be downloaded and included in the classroom, in a document or on a web page that the lecturer in charge of the subject or tutor produces without the need to request any type of authorization: the fact that it is on the Internet does not mean that use can be made of it freely.
The moral and property rights of a work belong to the person who created it, both if they specify this (eg by means of the © symbol next to their name) or not; consequently, it is considered by default that all rights are reserved.
If the image is used in the field of education, the possibility could be considered of using the citation right, which permits the inclusion in one's own work of external works subject to authors' rights to make educational use of it without the need to request authorization, providing:
They are works already disseminated.
The inclusion is as a citation or to make an analysis, comment or critical judgement.
It has teaching or research aims in a measure that justifies its inclusion.
The name of the author and the source of the work used are mentioned.
Despite the possibility of assessing this option, under no circumstance may images be included that do not have a license that has released the rights that permit use of it, and even in this case the source and author must be cited.