I strive to make sure that I'm operating within copyright law when it comes to using materials in my public postings. I have found it confusing when doing a plain Google image search to know what copyright requirements are for any given image. (Yeah, the images with the obvious watermarks are a good tipoff that they *are* covered by a copyright.) When I have checked into licensing images, I have found the prices to be quite high for someone like me.
Good news: I have found a great site for downloading free, high-quality graphics. It's called PhotoPin. They take the guesswork out of the process. You search, find, download, and follow their instructions for proper attribution. At the bottom of this post you will find an example of the attribution for the image at the top of this post.
The process is simple.
photo credit: lsten Secret Sunset via photopin (license)