In that time, I learned a lot about how their maps are generated and I wanted to take the time to share that with everyone. Let's start out with a familiar image that I've applied some edits to. If I list anything incorrectly, I apologize. It was quite late and I admit to not checking -everything-.
Layout - The overworld maps have a fixed border that does not change from game to game, though in large maps it may be difficult to gain your bearings. An area will typically have a few large blocks, and a few small blocks. These blocks are always in the same spot on each playthrough. Large blocks will always be found in the same place, small blocks will always be found in the same place. Their contents are what changes from game to game, but where they are found remains consistent.
Large Blocks & Small Blocks - While large blocks like the ones found in the Fields of Misery have yet to be found, an example of small blocks can be seen in the large patch of overworld on the way to the Cemetary. Here you'll find 4 or 5 areas that will be populated with various events, and are generally the only potential points of interest in the area. The Den of the Fallen is one of these, the Blacksmith's Apprentice is another, etc.
Variable Block - Another block type is the variable block. I'd say these are typically buildings, but can certainly encompass other fixed decoration locations. A good example is the first stretch of overworld map on the way to Old Tristram. You'll find several buildings that can either be open or closed, but you'll only find a few of them at a time. Two, I believe, between both the road and the town itself. These are slightly different from the variable block found in the Fields of Misery, in that Field of Misery's variable block always has something of interest.
Medium Blocks - The blocks found in The Festering Woods would mostly be described as somewhere between the large and small blocks of Fields of Misery. They are similar in size to the two blocks found in the halfway point of the road to Old Tristram.
Fixed Blocks - Fixed blocks also sometimes appear. You'll find the same event or decoration at a fixed block every time you load a game. "Bloody Lumberjacks" and the Memorial Stone are two examples.
Resplendent Spawn Points - Lastly, the edges of the map sometimes house a Resplendent chest. One does not always spawn, and there will only(?) be one spawned in an area at one time. The stars are the spots I found one, but it could possibly spawn in other locations in the area.
Please correct me in the comments on any names or details that I listed incorrectly or could not remember. Thanks guys.
Fields of Misery
Forlorn Farm - Loot the fallen beast, and an elite scavenger will spawn. Defeat it, and a male farmer will exit the nearby cellar and walk to your character. After speaking a line, he returns to the cellar and it becomes enterable. [Farmer's Cellar] Once inside, a voiced event plays out between him and your character. You will also find a Resplendent Chest here, however it is bugged and drops lower-than-appropriate level loot.
Forsaken Grounds - A man [Beleaguered Farmer] stands to protect his farm. Speak to him and four bat hives will be highlighted on your map. Attacking a hive will spawn additional bats from the woods, making them harder than normal to defeat. There is no completion reward for this event.
Secluded Grove - A Resplendent Chest waits in front of a large tree. Upon approaching it, your character exclaims it's clearly a trap. Opening the chest will drop items, but will also spawn "The Old Man" and 4 other tree enemies. This is a very challenging pack as their poison has the ability to kill you in ~2 seconds if you don't move out of it, and the entire ground will be littered in spores. NOTE: This is a highly farmable event, as it guarantees a goodie-bag chest. Runs for locations such as this will be a very strong option for loot-finding.
Decaying Crypt - This is a two level dungeon that ends with a quest. The dungeon layout on the first floor has two # shaped rooms with only one way out of them. The second level has the same quest each time. A ghost (Willa Rathe) will ask you to lay her family to rest. Father, Mother, and Little Jebby Rathe. The first two you kill drop 1 magic each, while the last one drops a regular amount of loot. This quest does end with a reward.
Unnamed #1 - A village in ruins and flame has a regular chest atop a hill with goatmen assembled around a non-special 'chieftan'. Mostly just a pretty block, nothing of note for loot.
Unnamed #2 - A small pond or lake. This block has nothing at all of interest and can be ignored.
Waypoint - One of the four blocks will always hold the waypoint.
Dungeon #1 - Unworking, blue aura facing left.
Dungeon #2 - Unworking, gold aura facing left.
Dungeon #3 - Unworking, gold aura facing right. This one has a corpse in front of it that directs the player to chase an enemy down inside the dungeon. Clicking it will spawn a few regular scavengers.
Lonely Dwelling / House of Curios - A rare block spawn that has a merchant inside. She will sell you various dyes, as well as usually having a rare item for sale. Rare items sold my vendors are visually shared by all players and have a total quantity of 1. The house also contains a lore book.
Scarecrow - Clicking the scarecrow will spawn two waves of bats, with the second wave containing an elite. Currently it is bugged and the elite does not drop loot. (Possibly intentional, but frustratingly so.)
Burning Tree - Decoration only. A charred tree sits in the middle of the block area.
Open Field - Decoration only. An open field that has a small random fence near the top of the block area.
Sheltered Cottage A, "Swelick's Corpse" [Probably misspelled] - A lootable corpse is found in front of the barricaded cottage. Clicking it will spawn a non-elite pack of scavengers. Nothing of interest.
Sheltered Cottage B, Tinker's Hovel - A bag lays in front of the cottage that holds a lore book. Inside, you'll find a merchant that sells potions and occasionally a rare item.
Sheltered Cottage C, [Bloody Chest] - Approaching the cottage, a goatman will burst through the door. Inside, you'll find several corpses (and rarely some goatmen) as well as a Bloody chest.
Abandoned Lumberjack Camp - Labeled in the map I found as Bloody Lumberjacks, your follower will apparently dialogue with your character at this location(?).
The Festering Woods
(I didn't explore this one nearly as thoroughly, so there may be incorrect or missing information.)
A: Sunken Cave - A little spot in the center of the map that you can shoot down into. A really neat effect. There are a few bats hanging around down there that will come up after you.
B: Memorial Stone - Clicking this will start an event that throws a few waves of monsters at you. It finishes with an elite shield-bearer pack spawning. No loot outside of the elite's.
Waypoint - The waypoint may be a fixed block here, actually.
Dungeon #1 - Possibly main-quest related.
Dungeon #2 - ???
Nephalem Monument - A voiced event that spawns friendly ghosts that are 'being attacked'. They fade, and a non-elite wave of monsters attacks you. No loot, but still rather cool.
Three Hives - The last block I can remember has three hives in it. A decent challenge for under-geared characters or split parties.
Decoration Blocks - I believe there's a standard blank or two to fill in for the remainder, similar to the path to the Cemetery's blocks. One pattern I know of is the same as the Nephalem Monument's block, but without it.
Edited by TobiasAmaranth, 14 March 2012 - 02:38 AM.