Everything good's been suggested already
I would suggest UberUpgrades, but 1. It can sometimes get too insane 2. The plugin is still WIP, and you can only download an older plugin.
So, how about a Halloween maps-only server?
I'd love me some Halloween
Or how about a 2nd custom maps server, but with the more insane and stupid maps, like TrainSawLaser or WubWubWub?