Canva has a library of free images that can be used.
Visit https://photos.gpus.org for photographs of Greens in action.
Visit https://www.istockphoto.com/ and search through the “Essentials” category, then send a note to wbmgr.org for what you need.
Visit https://www.loc.gov for historical images. Give credit for the source.
Go to https://www.google.com/ and enter a search term. From the next page select “Images” then Tools / Usage rights / Creative Commons Licenses. Be careful with the results as not everything is correctly licensed.
Note that many libraries and universities have special collections available for public use. Here is one example from Kent State University.