Murzstin's renders are made from Worlds, as seen from the render of Steve sleeping on a bed with an Island in the background (Seed "Artomix", 1.3.1)
and to my knowledge the seed from that world hasn't been found yet. On his YouTube channel years ago he uploaded a video where he showed how to make renders, in which he created "Steve wrócił z wakacji" (https://youtu.be/0jTxsHeTFG0?si=PZrRR0Pk6sRxv7IP). He exports the world and selects what part will be used for the render. Features of the world (image 3-4) and the game version (1.2.5) can be seen in the process.
Note that in the last picture there's a spot with Diamond blocks and a ravine with lava, which is where the skeleton is being pushed in the render, with the coordinates being shown in the lower left of the screen (x=86,753 y=70)
by Idk_whatname013