It really depends.

Maps that come with the game:

Aran 107 Provinces, 11 Under water
The Power of the Eye ** Special Victory Map
Time of Blood, Urgaia episode 1 ** Special Victory Map
Brittan 68 Provinces
The Desert Eye 125 Provinces, 17 under water
Flames in the East, Episode 3 ** Special Victory Map
Inland 154 Provinces, 5 Under water
Invaders, Urgaia episode 2 ** Special Victory Map
Oriana 279 Provinces, 20 Under Water
Wars of Orania ** Special Victory Map
The Sundering 61 Provinces, 10 Under water
Reemergence of Urgaia 59 Provinces

Special Victory maps are maps with victory conditions that are only playable with a certain number of people/AI with special sites and victory conditions for a varitety of ways to win.

A good download is the Seven Nation Rumble, World War, and World Map, availiable at IW's site I believe.