Someone taught me this trick a while ago - when needing an image free of usage rights:
Google whatever it is you are wanting the picture of, then click "images" , then click "search tools" , then click "usage rights" and then it brings down drop menu that has several options. You can then choose any of those, depending on what you want to use it for. If you are going to be changing it or something - obviously you need to choose it for "labled for
reuse with modification" - or if you are just posting it on permies AS IS, you can choose "labeled for reuse" or "labeled for reuse for noncommercial" because permies is noncommercial. but if you are putting it in an article, just to be safe, I would go with the one that lets you use them for commercial purposes.
This is a link to that for images of underground greenhouses.
They don't always have the BEST pictures, but a lot of the time they have what ya need.