In the era of copyleft and open source, there are still many cases when people steal images for their private purpose with no quoting, no link (or not followed link), no request for permission not to mention economic contributions.
If not the ultimate solution it seems an excellent resource for anyone looking for great, catchy, free, high-resolution images for #social media posting. The risk is that some of them might get very popular at the end, reaching an iconic status, but it worth trying unsplash.com, as I did here.
Here is their “legal stuff”:
All photos published on Unsplash are licensed under Creative Commons Zero which means you can can copy, modify, distribute and use the photos, even for commercial purposes, all without asking permission.