You can use images that you have not created yourself. Make sure that you always read and the use restrictions for your image sources and follow these. Also: always cite images someone else created (and your own as well).
Pics4Learning is a curated image library that is safe and free for education. Teachers and students can use the copyright-friendly photos and illustrations for classroom projects, web sites, videos, portfolios, or any other projects in an educational setting.
Make sure to use the citation information given with each picture.