If you don't have Reyk's editor and don't want to install mods, then you could try making a large random map with 12 players to work with. That's going to definitely be really close to 1000 or more.
Of course, this question has been asked and answered a few times before, so I'd suggest that you use the search function for questions such as these.
Just trying to help
regards
the Elder
"imagination is more important than knowledge."
Albert Einstein