The Fair Use clause of Copyright law allows you to use any photos or images you find as long as they are for educational purposes only and not for commercial gain. However, with any website or database, it's a good idea to look for a Creative Commons license checkbox so that you are sure you are welcome to use images you find.
Because images you find on databases or the Internet are the intellectual property of other individuals, you must cite your sources when you use images in your scholarly works, whether it be in a paper, a presentation, or art work you create.
Check whichever style guide you are using for proper citation format.
The citation should be accessible in the context of the image's use (within a Powerpoint presentation, on a web page, in a paper, etc.).
Image citations should include the following information:
Sometimes not all of these pieces can be found, so you may only cite what you know, but you must make a good faith effort.