dunGen is a Haskell command-line tool for generating random grid-based dungeon maps for D&D and other tabletop roleplaying games. Choose the size of your map and your desired density, and dunGen will render an image for you.
To build and run dunGen, you'll need Stack.
Build with stack build. Run with stack run. dunGen currently looks in the current directory for the dungeon tile sprites, so run the program from the images directory if you are using the default tiles.
As for parameters I'd suggest using
Grid Width: 40
Grid Height: 40
Density: 30
as a starting point.