Last Updated: 07 Oct, 2016 Views: 30
Creative Commons (https://search.creativecommons.org/) can help you search major collections of images licensed for reuse under a variety of conditions.
Click on the source you want to use (e.g. Flickr, WikiMedia Commons, Google Images) enter your keywords and press enter. Your search will be formatted to retrieve images that are likely to be licensed for for free re-use. Check the link to see exactly what you are allowed to do in terms of modifying, sharing and acknowledging the image's copyright holder.