Google image search can be used in a couple of ways.
If you are unsure if an image is in the public domain, drag and drop the image file onto the Google Image search page. The image will be analyzed and matches are displayed. Go thru the list for matches to stock photography web sites.
You can also use Google to find “free to use” images. Do an image search, then click on the gear icon options button (upper right), select Advanced Search, and scroll down to select the appropriate Usage Rights.