All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Supernatural characters in games and movies are prohibited if they include the claim of divinity and the characteristics of Godliness, such as resurrecting the dead and the claim of the absolute knowledge of the unseen, and so on.
What you mentioned by saying: “e.g., ice from producing liquid nitrogen or using body fats to make something tangible”, is apparently not forbidden.
As for inappropriate images: then if it is possible to prevent them so that they do not appear completely in the game, then it does not appear that playing the game is prohibited in this case, because the meaning for which it is forbidden to play is removed, which is looking at the forbidden images. Nonetheless, it is better to avoid playing with such games at all, so that the player will not be drawn into showing forbidden pictures and looking at them.
Allah Knows best.