I'm not sure. All I know is it's not wood.
Is it a wall covering, which could be anything from velvet to leather? It really depends on what the material is, otherwise you could make the problem worse. Can you put another picture over that spot? Not trying to make light of it, just saying if you can’t remove the stain, maybe it’s a nice place to put something else.
Are there homes in the neighborhood made with the same material? Maybe a neighbor would know.