I won't be able to make something quite this polished (especially on short notice), but here's a screenshot from Stardew Valley:
I was thinking something that looks a bit like that, but with darker colors and darker themes.
I think that style will work perfectly. Since it might be tricky to include jump scares or a horror theme in that style, Itll be better if its just a Christmas-themed game with a cute and cozy atmosphere. We can still include some mysterious elements, but more in a puzzle way.
Also, could you let me know about the cost for a project like this?