Actually, I'd strongly recommend taking your own photos of the things you write about. Cell phone photos work just fine. Capture a beautiful dawn/sunset, cute animals (dogs, cats, wildlife), etc. Your readers have seen all the same free photos before... Impress them with something simple that you created (shot)--if it's obvious that you, the author, took the photo I think the reader is more interested in what you have to say, also. Plus you can get exactly the shot you want. That's my $0.02 anyway.