I have actually been hoping to make a tutorial like this since it is a pretty common map type and there doesn't seem to be any one comprehensive tutorial on here yet. The only problem is, like DevinNight has said, a lot of it is pretty basic concepts and trial and error. There is a lot less procedural stuff/simple tricks that show up in regional/world maps, and probably a lot more artistry involved in making dungeon dressing (like DN's awesome objects). I hope to put something together in my free time soon, though! I'd sure like one of those little tutorial icons!