Check the image to see if there is copyright information. Not all images from the databases may be freely reused or used on commercial sites.
The default Powerpoint or Google Slide setups may not always work for your presentation. Some other sources you could try are:
Copyright is very important! When using images from the web, it's vital to make sure you aren't violating copyright law. The easiest way to do that is to use images that are either labeled with a Creative Commons license or available in the public domain. Always follow citation and attribution requirements for the image according to the license. See our Copyright Libguide for more information on this topic.