At a mini-game convention (it was just a couple hundred people), I DMed a "Kobold" adventure. The plot took place in a dark forest possessed by a humanoid-hating spirit, so malevolent and ruthless that all the surroundings have been closed, trapped, etc.
Inside, several tribes of kobolds are emprisonned and must survive. I had fun imagining what would look like a tribe's village in a place where everything -- plants, bugs, animals, etc. -- want your death. Traps, alchemical repellents, watchers, paranoia, and so on. It was fun!
And the kobolds were kick-ass, too.