Make sure you're fact checking all of your research, but especially information from these sources. Use appropriate search terms to help yourself sift through the myriad of results you're going to get.
Encyclopedia Britannica Kids
Encyclopedia Britannica Kids is a great source for information in a variety of forms. You'll have to scroll down to see the search area (and you may have to deal with a few annoying pop-ups encouraging a subscription purchase), but it's worth it for the wealth of information here!
There's an entire tab just for images and videos!
Discovery Education
Discovery Education has text, images, and multimedia content. Make sure you use the filters to narrow your results or you'll have a lot of information to sift through that may not actually be useful.
There are separate tabs for images and videos each.
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Google Images has advanced filters that can help you focus your search results. Be sure to read the captions and go to the source of the image or video instead of just skimming the results page.
YouTube can be an excellent source. HOWEVER, it is critical that you carefully evaluate the source, parallel research to fact check, and search wisely.