morgueFile is a free archive of photos. It’s searchable, and it’s got some really fantastic images.
According to the site’s license explanation, you can use these photos without proper attribution, as long as you don’t say they were taken by you. But I still think it’s a good idea to get into the habit of attributing. And it will be useful for your classmates if they want to use the same photos for a different project. Just make sure you stick to the “Free Photos” from morgueFile and double check that you’re allowed to use it. This is what to look for:
So if you want to brighten up your Summer Notebook or find a photo to help you explain something, go ahead and start exploring!