Some of my head-canon…
This is long, you’ll need a sandwich if you intend to read it, but boy howdy I enjoyed writing it down.
Azeroth is much larger than it appears in game, with vast areas that are largely unexplored wilderness, in some of which are animals and plants yet undiscovered by any of the peoples of the world.
Big cities like Orgrimmar, Stormwind, and Boralus have amenities you’d find in real life like theaters, meaning there are actors, stagehands, musicians etc on Azeroth (not just as ghosts in Kharazan). There are traveling actor troupes.
There are seasons, and some birds (including ducks and geese, which exist) migrate.
Stormwind - a large port city on the coast - earns its name in the rainy season.
Orgrimmar looks beautiful in winter, with the desert dusted with snow.
Thunder Bluff is temperate all year 'round, but the Tauren build large bonfires to warm their kin on the chilly bluffs during the winter months. Much of their culture is still nomadic and wander the plains of Mulgore (which are the size of Mongolia in my head) in caravans as hunter/gatherers.
Farming is much more prolific than it’s depicted in-game, and the economies of the Horde and Alliance are mostly agricultural.
Many (but not all) characters who are of the class “Hunter” are actual hunters, who make a living hunting and trapping, and they track different types of animals with different seasons.
The rich nobles of for instance Stormwind are from families whose hands have not touched dirt in generations, until the Third War, after which some lost everything and now wander the streets homeless.
Silvermoon is mostly re-built, but not completely. Some of its damage can be seen, from certain angles; some of the reconstruction is a magical “glamor” which can be seen through, from certain angles, revealing cracks and lost architecture.
It’s always the last days of summer in Quel’thalas, with the leaves just starting to turn and fall, because the Blood Elves glamored the woods to appear so. In reality, the devastation is much greater and trees are only now beginning to return to the blighted land.
Death Knights are rare, and since the events of “Wrath” and their re-introduction into society, folklore has sprung up around them, including it’s considered bad luck to see one in your town or near your home.
Vol’jin was Warchief for five years, and prosecuted major campaigns against an alliance of quilboar and gnolls who harassed the Mulgore tauren. At the height of the crisis, Thunder Bluff was cut off, and Vol’jin peronally led the troops who broke the siege and saved the city. Baine considered Vol’jin as his own family after this, and there is a statue of Vol’jin - now considered a folk hero among the tauren - in Thunder Bluff to this day.
Theramore was the size of Stormwind, and its population contained the greater part of the High Elves remaining. Its destruction reduced their already paltry numbers to a few hardy, increasingly traumatized survivors.
The greater numbers of Forsaken are aware of themselves as cursed, they do not relish being Forsaken, and the idea of visiting their “disease” on others is anathema to them. Some among them though have embraced darkness and wish nothing but ill on the rest of the world. They’re not monolithic, and though many did, many others never followed Sylvanas like she was a cult leader.
The Exodar has been largely repaired for years, though cracks remain. It lacks armanents and is not useful in battle as more than a troop transport. It was used - too late - to help evacuate Night Elf and Gilnean refugees from Darkshore at the start of the Fourth War, and now hangs silently in the sky just north of Stormwind. Teleporters aboard transport people between the vessel and the city below.
After the events of the Broken Shore, Genn considered turning on Anduin, though he quietly loves him as a son. Genn felt Anduin was not the right choice to prosecute the war against the Legion, nor to handle the Horde, especially with Sylvanas as its new Warchief. Genn’s plan was to accuse Anduin publicly of being not Varian’s son, but the illegitimate son of Arthas Menethil, stripping Anduin of his claim to the throne of Stormwind, arresting him, and placing him in the Stockades. Greymane touched on the subject indirectly with S-7 leadership to gauge their support, but was rebuffed. In frustration, he decided to press an attack on Sylvanas directly, leading to the events of Stormheim.
During the Fourth War, the Night Elves briefly planned dual-suicide attacks on the Arcan’dor in Suramar - to destroy the tree and reduce the Nightborne back into wretched husks depriving the Horde of their strength - and on the Sunwell itself in Quel’thalas, to do the same to the Blood Elves.
Anduin learned of the plot through S-7 spies, and directly forbade Tyrande from carrying it out, considering it a “crime against sentience”. Exposed, the attacks didn’t go through, and only Shandris’s pleas kept Tyrande from murdering Anduin and attempting to claim the throne of Stormwind for herself, to throw the full weight of its armies - including the Vindicaar - against the Horde.
Velen learned of the plot, and quietly made sure the Vindicaar was secured and “unavailable” to take part in the Fourth War, not wishing to see it turned into a weapon of mass destruction, when it was built to defend all of Azeroth. Greymane was quietly outraged at Velen’s actions.
The Night Elves took not just Mount Hyjal, but all of Hyjal, looming to the north of Orgrimmar. Though there is an armistice, any Horde citizen traveling to Hyjal does so at their own risk.
There’s no portal in Origrimmar nor Stormwind which leads to the afterlife. Those in the Shadowlands at present are trapped there until the story’s resolution. On Azeroth, the Scourge run rampant, and the armies, adventurers, soldiers for hire, and even ordinary folk are desperately trying to stave off the greatest threat since the destruction of the northern Eastern Kingdoms. Those who went to the Shadowlands are considered lost and presumed dead.
The Darkmoon Faire never closes.