Halloween is usually the following items:
Silo
Recycling Manufactor (this might be Christmas I know it's either Halloween or Christmas)
Village School
1 Grim Reaper
and they will put grout in.
I honestly would like to see improvements in the game, ie general skill tree. Home Island Skill tree, or other level 6 buildings. Or have a way where you can stack items within the star menu. Or up the quantity of troops/provision trained instead of at 25. I know all this is doable. Instead of "introduce new buildings", start giving us what Settlers promised yrs ago.