This is official art used in covers and promos for the game, produced by the Art Director of the game, Jen Zee. However, there was never a tall portrait version of it…

I’m speculating, but looks like Igor Artyomenko expanded on the piece. So in this case, things are the other way around, this is not a crop of Igor’s art, rather Igor’s version is a derivative of Jen Zee’s.

Edit: I might be wrong. Igor’s post is from before the game came out, and now I can’t find the piece from any supergiant source. The pieces style matches that of Jen so closely it might have gone unnoticed by most, including me, that it wasn’t an official art asset.

Edit 2: Danbooru credits Igor as well. Good sleuthing Crul!