Not sure if it’s been touched on or not, but I do notice that “portraits” seem to be a part of the game again. I haven’t seen or heard anything of actual portrait ghosts, but there are portrait frames on the official site. http://luigismansion.nintendo.com/characters/

Also, seen a few instances where the dark light (think that’s what it’s called….) can be used on a portrait frame. Just an observation.