Okay this is how you get l4d custom maps go to www.l4dmaps.com and you should find a bunch of custom maps you can upload maps to just go to the tools and download the left 4 dead custom map tool sdk thing youll download it and create maps and then go to the website and upload the map file if you want make code blue gamers maps just make sure the map name is L4D_CdB for the first part of the map name.