These are from artist Jakub Rozalski, who posted these on his Artstation page. You can view more of his work here . Check out the synopsis and images below.

"Kong ruled in the cinemas around the world, so I think I can share some of my favorite illustrations & concept arts I did, more than two years ago, at the early stage of the visual development of the Kong: Skull Island movie. It was amazing adventure, great experience and at the same time my last work on non-personal project :] Big thanks to the director Jordan Vogt-Roberts for the trust and this amazing opportunity!"