We've made a bonus generator for Worldmaker that makes a Halloween-themed map full of Jack O'Lanterns, spider web trees, and spooky houses
You can download it here: http://www.startreegames.com/WorldMaker/
We'll only make this one available for a short time, so get it now if you're interested. This map is better for a Halloween party than it is for building anyway, though you could try it either way.
Here's a couple of screen shots to give you the idea:
I make map generators