This hack looks pretty nice. I'm not a big fan of the custom graphics you used though. The ice blocks you used for the landmasses here
or for the castle blocks here
look rather boring to me (especially the castle blocks look very monotonous). I think, since the vanilla dirt worked for the first 2 screenshot, vanilla gfx could be used here, too perhaps? On the other hands my complaints may be totally subjective and only my personal taste, so there's perhaps no real need, to take it too serious.
But i at least wanted to give you my opinion, since this looks like a quite enjoyable hack (i agree with Veck: I like the festive theme lots as well) and perhaps my feedback can you help improving it a bit more.