In older versions of D&D they provided some basic guidelines for stocking new dungeons or restocking dungeons that had been left idle or abandoned by the players. These rules were more useful in the days when modules were rare or expensive and budding DMs were forced to use their limited skills and imaginations. There is a nice little summary of methods used between editions here: http://deltasdnd.blogspot.com/2012/10/random-dungeon-stocking.html
Here is also some newer interpretations of the idea with sub tables in practice should you wish to investigate further.
http://aeonsnaugauries.blogspot.com/2011/11/dungeon-stocking-table.html
Thanks again for the generator by the way. I have used it to flesh out two mini side treks in a sandbox I'm developing. It really is a wonderful tool.