Hi sinzz,

Sometimes when we update our content Garry's Mod can take a while to catch up. If you see missing pink/black textures or receive a "Missing content message ". Follow these steps to fix it:

1) Unsubscribe from the HALLOWEEN CONTENT pack: steamcommunity.com/sharedfiles/filedetails/?id=332403428
2) Delete all files in garrysmod/downloads/server/
3) Restart the game and re-connect to the server the updated content will be downloaded automatically.
Enjoy!