Learn to structure a detailed Search Query to find a valuable resource

Say you want to find a public domain image of something. This is not as easy as you might think. Various "free license" like GNU license images abound, but the licenses require attribution, which is not always what you want to do. You want a good picture and you want to find it fast.

But that's not all you want. Ideally, you want to search in an image search engine like Google Images, so you can see a thumbnail before clicking.

For example, you might like to structure a query like this:
flower site:commons.wikimedia.org "in the public domain" "jpg - Wikimedia" OR "jpeg - Wikimedia" OR "png - Wikimedia"

And that would be pretty helpful, but there's no thumbnails, as it doesn't work in Google Images.
Update: above query does work in Google images now! And it's a good one!

So a bit of searching tells us that on openphoto.net, public domain images are tagged with "PublicDomain". So we try this on Google Images:
flower site:openphoto.net PublicDomain

But we find lots of links to index pages that we don't need. So we go back to the image pages themselves to find an identifying piece of information, so we can let the Search Engine know exactly what we are looking for. And we find that the picture pages themselves always have "openphoto.net" in the title, but the unwanted index pages do not. So we settle on a query of:
flower site:openphoto.net PublicDomain intitle:openphoto.net

which works! Page after page of thumbnail, and it's easy to find one that suits our project.

Next time: How to find any video file