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!"
"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!"