For free images, vectors, illustrations, and videos to add spice to your articles, Pixabay is one great resource. You are free to edit and reuse even for commercial purposes. The pictures are beautiful and high quality that it’s hard to believe they’re free.
Some images are published with the Shutterstock logo, though. Marketing Shutterstock’s paid image services could probably be one of the site’s sources of income, so no harm done there.
All images there are free to use. You can search for images, then download the one you like onto your computer. Afterwards, you can add it to your article. There are a few other sites like Pixabay, which provide images for others to use, but I can usually find what I need on Pixabay and have rarely needed to search elsewhere.