I think a fun idea would be for us to be able to buy pumpkins in-game that we can "carve" with our own designs and put the resulting Jack O' Lanterns outside our doors :)
Or if using our own designs wouldn't be possible, having a selection of templates to choose from. Piggy or Rube or Giant - or, for the Glitches that prefer their Halloweens creepy, Rooks or Jujus.
I don't know if the game acknowledges Halloween, since they have their own version called Zille-o-ween.
Which just passed not that long ago, unfortunately.
I don't think that any real life holidays are celebrated in the game. But they did make some of their own versions of holidays which are Glitchified. :-)