Image by Pexels from Pixabay
Pixabay.com is a stunning library of free-to-use images for commercial and personal purposes. They do require registering for an account if you download full-sized images. There are some restrictions on how you may use their images but for most purposes, it works very well.
Creative Commons is loaded with current event and historical photos and has a handy search tool to help you find images to use for commercial purposes. Be careful that you read image licenses carefully because not all Creative Commons images are free for use.
Freepik has an impressive collection of stock photos, templates, and mockups that are free for use with proper attribution. They have an extended collection of images available for paid licensing on a subscription basis. Like Pixabay, there are restrictions on exactly what ways their images can be used so be certain to read their licensing agreement.