Zombicide has a new mission and map editor available over on the Guillotine Games website.
From the update:
This editor was born from the open-source software Mapeditor and fit to Zombicide by Mzi and Rogue. A great thanks to them!
The name says it all: this software allows you to create your own missions and share them with other players. Choose your tiles, doors, tokens, arrange them to suit your fancy and give new challenges to your survivors’ team.