Are you looking for images to use in your PowerPoint presentation, lecture, or research paper? Before using an image from any resource, read the license information listed at each site and, as always, credit the author! Here are some best practices:
Tables, graphs, etc. are also images and should be cited as well/ This can be as simple as a URL beneath the image or some word or phrase leading the learner back to the citations at the end of the presentation.
Cite the original source of the image. If you use an image from Google then try to trace the image back to original creator.
Be consistent. Cite images in the same manner throughout your presentation/scholarly document.