Another spawn of mine that was created without request. It can be repeated as tall as you want (as long as it's within the chunk limit), just use MCEdit to select the top two layers, copy them, and repeat the copied selection all the way up.

This spawn takes up exactly 1 chunk, fits to the boundaries of 16*16*x (x=Any height), and is a quiz spawn.

To the LS thread:
www.planetminecraft.com/forums/creating-free-survival-server-spawns-t103271.html