Since it hasn't been officially stated here for a few days after it was announced on MineTowns Discord chat server. Here is Bumpy's post from Discord.

No news as of yet.

My current skin is essentially my regular "Game Sprite" skin but corrupted. Undead for digital beings? I'm not sure if this applies to traditional "Halloween themes" but I figured I'd chime in anyways since I went ahead and made this at the beginning of October in preparation for Halloween. You may disqualify my entry if you feel that my skin doesn't meet the Halloween theme requirements. The first image I attached is the normal skin I use for comparison.

I can confirm that you can do this in the museum servers.