Something I just noticed:
When I make my layouts on paper, or digitally I apply lots of imaginary rules to them, for game play, and to keep them looking interesting. Like not to keep one path going for too long without variation or entry to another path. Also to keep everything rather logically done, even if the level is set in nature there is no reason it has to be done randomish the way nature would really be. if you had enough of these rules you could probably make a layout generator.