I'm not so sure about Halloween, there were pumpkins around in this event that just ended.
But I'm pretty certain that there will be one of those short events (lasts about a week) that they have before the long winter event in december. When exactly is just guessing, but I wouldn't bet it starting right after a long one which is only just closing in live servers.
Wow, ok then. Now I've started to remember - there was an event that had a graveyard thing as a prize, and maybe some kind of a shack also.
Didn't take part in that one.