Adobe Stock
Questions & Answers

Dreamstime.com I get premium images or try their free section every once in a while. There are other free sites, but the content here is more unique. Also Stockfreeimages.com is a sister site I use frequently, tons of free stuff sometimes not easy to find though.

You can try Unsplash I think it is called. It's a free stock images site. They don't have the selection that Adobe does but they do have a lot of images. It just depends on what type of photos you need