Ahh this is my favorite question to answer! In fact Ive been asked this question so many times I created a FREE email course to answer this very question (and others related to using photos in slides) Create Your Visual Database It might sound weird that I made an email course about this but here the thing 1. Ive checked out a LOT of different sites that provide free high quality visuals. There are only a handful that I actually rmend spending any time sorting through some of them are filled with garbage s you need to cite the artist some you don and there is moreplexity in between (such as whether or not you can modify the image). 3. If you make a lot of presentations it easy to end up with a disorganized mess of photos where you end up wasting a lot of time looking for photos you already saved etc. The email course is also designed to set you up to be organized and efficient. People seem to like it so far (yay!) Create Your Visual Database If that too much right now then I give a +1 to the person who said Unsplash | Free High-Resolution Photos that a pretty good site )