The Land of the Giants. The broken archstone. The level dug up by hackers in recent years in its very unfinished state. It's a large cold place. Nothing else in Demon's Souls is covered in snow.
edit: I am now realizing that having Bluepoint create an entire new level for someone else's game seems very unlikely. Regardless of there being a new world to explore they are one of the best Remastering studios. They did amazing things to Shadow of the Colossus for the remake. Crossing my fingers that they worked alongside Fromsoft developers to create the Land of the Giants, but I know it would be unprecedented and is pretty much not a possibility.