If you're looking for images to use in a presentation or report, it can be a real pain to try and find ones that you can grab without legal problems. LibreStock is a free multi search engine that will check through over 40 different websites to find images that you can use. I quote from the site: "I know it's hard to understand complex legal licenses so let me break it down for you. all the photos indexed on LibreStock are licensed under the Creative Commons Zero license. this means you can use these pictures freely for any legal purpose." This means that they are free to use, even commercially, you can modify, copy and distribute, and you don't need to attribute.