147456 Chunks of Desert and Dungeons and a large 256 chunk wide boarder around the desert map
the reason for its size is so the server doesnt need to work hard expanding the map when the servers processing is needed processing other things.
on a lot of servers with fly enabled grievers fly in 1 direction at maxnspeed, once they get to the edge of the map the server needs to work hardnexpanding the map which causes lag after a few minutes of themnpassing the boarder, by having a large pre-expanded map it may take grievers anvery long time to get to the edge so they may quit before they get there and ifnyour using a map boarder which can stop the map from expanding its still good to have a large map so you have a large area to explore andnit doest make players feel like the server is limiting where they canngo because I dough normal players will ever see the edge of a large map.

Additional Notes

Size Medium and Large will be out soon

if you like this or want some more maps check out some of my other projects

http://www.planetminecraft.com/project/planetoids-for-server-small/
http://www.minecraftworldmap.com/worlds/hyNUs
http://www.minecraftworldmap.com/worlds/lUWy8