A picture is worth a thousand words.
Appropriate use of images can often help your reader understand your content by providing a different way of connecting ideas or illustrating your arguments. Not to mention that they often make reading a more pleasing exercise.
Finding copyright-free images that you can use on the web can, however, often be difficult. Just because you an image is downloadable from the internet doesn’t mean you can use it legally, even if it is for teaching and learning purposes. You must make sure you are not violating copyrights or any terms and conditions stipulated by the image owners before using any images downloaded from the internet. The use of some images might require you to obtain model or property release even if the image is free.
To help you get started, below are some copyrights free image resources. Before you use any images, you should read the instructions for citation. The University of Chicago Library has some resources on how to do image research and provide citations. They are linked to at the end of this post.