These are the four official map packs for Emperor: Battle for Dune, released by Westwood Studios, produced in August 2001, and released between September and November 2001.
Note on nomenclature: Map Pack 1 refers to the original maps that shipped with the game. Map Pack 2 was automatically included in the v1.08 patch.
Map Pack 3
Map Pack 4
Map Pack 5
Map Pack 6