I was going to agree with @Robert Nicholson on using Google for image searches, but I had not seen the "labeled for reuse" dropdown before on Image Search, so I decided to check it out myself. What I'm seeing, which is typical of Google, is a menu of images that can be found on other websites. After all, Google is a search engine.
@Finnian, and anyone else, my recommendation is, if you're going to use Google to search for images, to, first, use the "labeled for reuse" option as it is not limited to noncommercial (there are two other search filters for those choices). But I also recommend actually visiting the site where the image is being drawn from.
Google, being a search engine, only gives you search results based on criteria that you set as a searcher. As good as it is, it isn't perfect. You still need to do your due diligence.
A lot of sites I see recommended are Wikimedia Commons, Pixabay, PublicDomainPictures.net, Pexels, Flickr, etc. What you need to know is each of these sites have their own terms of service and licensing agreements, and it's possible that different images on the same website could have different licenses. In the case of Pixabay and Pexels, all images are free to use without attribution, but some websites may use a Creative Commons licensing system, and others may simply have their own house license that they offer. So you'll need to read the terms of the website you get the image from. DO NOT DOWNLOAD THE IMAGE FROM GOOGLE'S SEARCH RESULTS. That could be a hot water recipe.
Only after you are certain of each image's licensing on the website that has the legal right to issue such a license (Google does not), only then should you download an image and use it.