Maps (EU2012)

XCOM: Enemy Unknown features hand crafted maps, there are 91 maps in total. Out of these, 29 are variations on the same map (example: Escort mission or Abduction mission on the same map), leaving 62 individual maps. The Slingshot DLC adds 3 new maps.
There are 6 types of UFOs in the game, and each of these has variations in surrounding terrain, but the same UFO interior. If these maps are regarded as a variation on the same ship, then there are 41 unique maps with no repeating elements or theme.

Map List

Abductor Cliffside Abductor FarmOutskirts Abductor_ScorchedEarth Abductor_WindingStream IntroLevel AlienBase01 AlienBase02 Bar Battleship_01 Battleship_02 Boulevard Boulevard (European version) CemeteryGrand Commercial Alley Commercial Restaurant Commercial Street Confounding Light (Slingshot DLC) ConvenienceStore Demolition FastFood Gangplank (Slingshot DLC) GasStation

Highway1 HighwayBridge HighwayConstruction HighwayFallen Industrial Office LargeScout_CreepyForest LargeScout_DeepWoods LargeScout_ForestTrench LargeScout_Hillside LargeScout_Stonewall LargeScout_TheBarrens LiquorStore Low Friends (Slingshot DLC) MilitaryAmmo Museum Museum (European version) OfficePaper Overseer_Deepwoods Overseer_ForestTrench Overseer_StoneWall Overseer_TheBarrens PierA PierA (Asian version)

PoliceStation ResearchOutpost RooftopsConst RooftopsConst (Asian version) SlaughterhouseA SmallCemetery SmallScout_Badlands SmallScout_DirtRoad SmallScout_Marshlands SmallScout_Quagmire SmallScout_River SmallScout_RiverValley StreetHurricane StreetOverpass SupplyShip_ForestGrove SupplyShip_OverlookA SupplyShip RockyGorge SupplyShip_Wildfire TempleShip TrainStation Trainyard Truckstop

By Mission Types

UFOs Crashed SmallScout_Badlands SmallScout_DirtRoad SmallScout_Marshlands SmallScout_Quagmire LargeScout_DeepWoods LargeScout_ForestTrench LargeScout_Stonewall LargeScout_TheBarrens Abductor_Cliffside Abductor_ScorchedEarth SupplyShip_OverlookA SupplyShip_Wildfire Overseer_Deepwoods Overseer_ForestTrench Overseer_StoneWall Overseer_TheBarrens Battleship_01 Battleship_02 Landed SmallScout_River SmallScout_RiverValley LargeScout_CreepyForest LargeScout_Hillside Abductor_FarmOutskirts Abductor_WindingStream SupplyShip_ForestGrove SupplyShip_RockyGorge

Abduction Bar Boulevard CemeteryGrand Commercial Alley Commercial Restaurant ConvenienceStore Demolition FastFood GasStation Highway1 HighwayBridge HighwayConstruction Industrial Office LiquorStore Museum OfficePaper PierA PoliceStation ResearchOutpost RooftopsConst SlaughterhouseA SmallCemetery StreetHurricane StreetOverpass TrainStation Trainyard Truckstop

Terror Bar Commercial Alley Commercial Restaurant Commercial Street ConvenienceStore Highway1 HighwayFallen MilitaryAmmo PoliceStation StreetHurricane

Council Bomb Defusal CemeteryGrand HighwayBridge TrainStation Trainyard SlaughterhouseA Escort Commercial Alley PierA ResearchOutpost Extraction Boulevard Museum HighwayFallen Assault CemeteryGrand Industrial Office PierA ResearchOutpost StreetOverpass Truckstop Slingshot DLC Low Friends Confounding Light Gangplank

Plotline IntroLevel PierA AlienBase01 AlienBase02 TempleShip

Unconfirmed = Listed on the DefaultMaps.ini file, not yet seen on the game.

By Daytime

Day Missions Commercial Street (Abduction) ResearchOutpost RooftopsConst Trainyard Truckstop Abductor_Cliffside Overseer_Deepwoods Overseer_ForestTrench LargeScout_DeepWoods LargeScout_ForestTrench SmallScout_Badlands SmallScout_Marshlands LargeScout_Hillside Abductor_WindingStream Abductor FarmOutskirts SupplyShip_Wildfire SmallScout_River SmallScout_RiverValley SupplyShip_ForestGrove SupplyShip RockyGorge TempleShip

Night Missions Abductor_ScorchedEarth IntroLevel AlienBase01 AlienBase02 Bar Battleship_01 Battleship_02 Boulevard CemeteryGrand Commercial Alley Commercial Restaurant Commercial Street (Terror) ConvienienceStore Demolition FastFood GasStation Highway1 HighwayBridge HighwayConstruction HighwayFallen Industrial Office LargeScout_CreepyForest LargeScout_Stonewall LargeScout_TheBarrens LiquorStore MilitaryAmmo Museum OfficePaper Overseer_StoneWall Overseer_TheBarrens PierA PoliceStation SlaughterhouseA SmallCemetery SmallScout_DirtRoad SmallScout_Quagmire StreetHurricane StreetOverpass SupplyShip_OverlookA TrainStation

By Continents

North America Bar FastFood GasStation LiquorStore PierA PoliceStation Truckstop

Asia PierA RooftopsConst TrainStation Europe Museum StreetHurricane

Source: DefaultMaps.ini game file - these settings appear deactivated.