Hello guys, I would like to update my older post - At the moment I share 200 Free HDRi skies 4k resolution on my new site. Its is my second source after http://texturify.com/.
You can have a bit taste by checking Free full size hdri sky 15k with matching backplates, that I share by direct download. Here is the link: https://goo.gl/KTFGDL http://hdri-skies.com/
Enjoy!