No, I've never used the "image" icon. The original way to copy stuff went through several iterations, but it entailed making a partial screen copy that included what you wanted to post. I think in PC you "snip" what you want. Mac works a little differently.
You'd do that, save the image to your desktop, and give it a name. Then you'd upload it to your Image Gallery, copy the "embed" link generated, and paste that into your post.