We already have half the items required for a 'spooky or horror' theme and there are already many parks on Youtube that work very well with such a theme. We have smoke and steam effects for atmosphere, we have props like the skeletons and skulls so it wouldnt take much to be added, maybe some anachronistic witch or ghosts, to finish it off.
Check out this amazing creation to see whats already possible,
[video=youtube;u9-OLhoH2Xg]https://www.youtube.com/watch?v=u9-OLhoH2Xg[/video]