As Scholars, it is unethical to simply copy & paste images from unknown origins! You should know where they came from AND ALSO give credit to the images in the same way you would quote & give credit to words.
Not every image you see is okay to use! Look for images that are LICENSED in a way that shows the creator WANTS you to use them! Some key words to look for:
Library databases recognize that you're using these for academic purposes and have built-in citation tools!