Post your ideas about the stories behind the multiplayer maps, such as: What is the structure in the distance on Ridgeline. What did the machines on Avalanche do? What purpose did the Blood Gulch and Battle Creek bases serve?
while not all of them can be answered, the halo wiki does provide some background for the maps.
The Defiant Map Pack maps Condemned and Highlands probably had the coolest backstories, since they were based on locations in the Fall of Reach.