Done some edits to the list. Not ready for the Shadowland tour but here are some basic story details.
Shadowland's story is that it is the stronghold of the villians and the villians, led by Maleficent, have eyes on the rest of the park to conquer. This underlying story appears throughout the park in minor ways(The Raven in Haunted Mansion will actually be Diablo, keeping an eye on the Phantom's operations for Maleficent). Shadowland itself is completely outside the berm, except for the Jolly Roger's sailing on the Rivers of Magic, and Nightmare Before Christmas which has a load RIGHT at the park's berm and the land's entrance. The villian's plans and the list of Evil Operatives in the Disney Legion of Doom can be seen within the queue for Bald Mountain with the ride itself being an attempted escape from the villians who instantly deem you spies of the Mouse. There are some good characters within the land of course, such as the Bats in Dragon's Keep or Sora and friends in Kingdom Hearts(which itself will have three entrances, Light within Fantasyland near Mermaid Lagoon, Dark within Shadowland, and Twilight near the berm further up from the Light entrance.)
The park itself as a whole I'm trying to make more of a community created by the cardinal realms where the Disney characters live and work together, though again, the Villians try to shatter apart. Streetmosphere type shows play a HUGE role throughout the year be it little things within the lands to annual events. Halloween and Christmas are the really big holiday events. In October, the villians really manage to succeed and "conquer" much of the park as overlays to some attractions come in. The story at Halloween is that in bringing Halloween to the park, Jack Skellington has inadverently allowed the villians into the park, as told within the rope drop ceremonies in October. Mickey and Jack ask guests to help set things right as the day goes on.
Main Street is the least affected. Outside of some basic Halloween decorations in the town, Jack Skellington and fellow Halloween Town residents wander, telling guests of the danger the park is in and to help free the Magic Kingdom from the evil.
In Frontierland, Alameda Slim has managed to buy up Thunder Mesa, the latest aquirement in his whole real estate scheme, and his fellow outlaws take over the town and the Western River Expedition and Big Thunder Mountain.
In Blue Bayou, the Haunted Mansion staff is throwing a month long Halloween party that the Phantom ends up successfully crashing. Critter Corner though is mostly untouched though they are having a Harvest festival.
In Adventureland, Dinosaurs have been released from Pelucidar(from the Tarzan stories and featured in the TV show) into Deep Jungle by Scar's Hyenas for more support in trying to oust Simba. Dinosaur animatronics appear in the Jungle Cruise, primarily in the form of Velociraptors. Agrabah is under Jafar's control and Barbossa and Long John Silver have successfully pillaged Pirates Cove, menacing guests standing in their way.
Fantasyland truly is hit hard as Maleficent's thorns rise throughout the area(however these are inflatable and are brought down after the last showing of Fantasmic for the night as the villians are driven back into Shadowland) and numerous villians and Heartless roam the area. The Dreamport is mostly hit by a large surge of nightmares as in the altered preshow, Dreamfinder notices the larger concentration of them and he and Figment warn us of the danger. Mermaid Lagoon mostly falls under Ursula's control as Poor Unfortunate Soul polyps appear in droves. Destiny Island's has a mystery trail set up where Heartless appear to shock guests.
In Toonopolis, Judge Doom have taken over much of the town with Dip Barrels appearing in Mickey's district while a Halloween show is held outside of Monsters Inc, though Randall tries to ruin things.
Tommorowland has fallen under Zurg's metal gauntlet, getting some help from the Empire and the Xilians, whose craft float over the attractions. Stormtroopers march throughout the area, interacting with guests.
The actual Shadowland tour will come soon, but it might not be tonight though...