QUOTE(Dawg)
Building on Installation tileset
Simply find the unused tiles in the tile palette using starforge or scm draft and use that as terrain. These tiles were unused but blizzard forgot to get rid of them. So anyway these secret tiles can be built on. Cool Huh.
Go into the tile palette. Tiles that work are tiles that are number 16-0 through 50-0.
Thats what dawg has posted for me to add to my big map help thread.
Use the nuke AI to nuke the location centered on the guy.