Warning to Single Players!
All of the maps can be played in single or multi player, at your discretion. However, some maps are specifically aimed at the multiplayer side of the game.
Balanced
This script guarantees the key strategic resources are near all civs, knocking out the "risk" to certain civs who require resources for their Unique Units.
Mirror
This script is aimed at 1v1 or two-teams play. It's a wild thing to play in single player!
Hub, Ring, and Wheel
These scripts are completely artificial, intended to supply balanced environments for MP action.
Team Battleground
The name says it all! This is a "deathmatch" map for multiplayer, aimed at quick, brutal gaming.
Warning to Multiplayer Players!
All of the maps can be played in single or multi player, at your discretion. However, some maps are specifically aimed at the single player game, while one or two require some additional warnings.
Continents
Soren has described this map as the "anti-MP" map. It is our most random, least predictable map. Of all the maps in the game, this one is the least well-suited map for multiplayer games involving teams. It is also the default map for single player. The behavior is nearly identical to Civ3's "Continents" map setting, creating a random number, size and shape of continents. Civs will start on the largest/richest of these and usually have multiple civs on any large continents.
Terra
This is the largest map script in our core group shipping with the initial game. I know some folks on the Civ3 forums caught wind of the notion that Large and Huge map sizes would be a little bit smaller than comparable maps in Civ3, but it just isn't true for this map type. Terra is gargantuan, and in fact, like the Earth Map scenarios, it may not perform well on older or slower machines. Terra produces earth-like worlds. There is one large continent where all players begin. This is equivalent to Asia, Europe, Africa and the East Indies all rolled in to one, but it is produced randomly and will vary to a significant extent. A second continent akin to the Americas is lost out in the fog and will not be reachable until ships can safely cross long ocean distances. There will tend to be some smaller landmasses akin to Australia or Antarctica that may or may not be reachable prior to oceanic shipping. Soren thinks this would be the ideal PBEM/Pitboss map and he may be right. At the very least, though, it is not a likely candidate for normal use in MP, being slower in almost every measurable way!
Custom Continents
If you choose "One Per Team" setting, this map is akin to a "team version" of Islands and is very friendly to multiplayer gaming. Any other setting will tend to produce incongruous starts! This is a map chiefly aimed at the single player crowd! Use anything but "One Per Team" at your own risk.
Maze
This is a novelty map. If it's not your cup of tea, don't complain. Just move on to something else!
Mirror
Some options on Mirror can be jarring to the uninitiated. Try playing with the defaults first. Also, if you do use Mirror options, it is a good idea to familiarize yourself with what the options do so you know what to expect! This map type should be great for "fair" ladder matches, but again, it is best if you know what you're in for. Please review the sample image!
Afterword
I hope you find this resource useful. This is an eleventh-hour reference guide written in English and not able to be translated for the initial release. Sorry about that! However, I kept on working on adding more maps or improving our existing maps literally right up to the deadline for new content.
It is my hope that generous and capable fans will translate this in to the other languages and make it readily available to non-English speakers.
I hope you enjoy Civ4, and that you get the most out of the map selections and offerings.
Added: Here are the civ4 mapscripts.