I hopped over to the Petopia link you supplied and took a look at it, and I'm going to guess it was concept art that didn't get modeled for Wrath of the Lich King. If you remember questing in the Western Plaguelands, there was a string of quests that made it very clear the wildlife of the region was being impacted by the plague as well. Maybe not in the same ways that it harmed the humanoid races, but there was an impact nonetheless.
This was probably just a concept art, but they decided to go with the orcas you see off the coast of the Howling Fjord instead.
It's really not uncommon to find copious amounts of concept art that never turned into anything in the game itself. There's a ton of it in the art books that came with the various Collector's Editions of the game and expansions, and I can lose hours of my time digging through the Sons of the Storm galleries. For example...
"Can you fly from Hellfire Peninsula to the Netherstorm over the abyss in Outland on your flying mount?"
Yes. It even counts as its own little zone. Your channels will switch from Hellfire Peninsula to Twisting Nether before becoming Netherstorm.
"In the Azeroth there are siege engines, guns, helicopters, robots, motorcycles etc. Since that type of technology exists why would anyone continue to ride on a horse or dragon? They smell, they poop, they need food, it's silly."
Do you really want to lay your cushy behind on a giant hunk of metal wrapped around a Goblin-made engine? I don't. I'll stick with my gryphon, thank you.
"When the new arena season starts will honor reset?"
No, honor points do not reset with new arena seasons. Arena points do, but honor points do not.
"How do gold sellers get all of the toons that they use for these marches/dead body graffiti? Do they buy that many trial accounts? Hack into character creation servers? If this is the case, how safe is the rest of the process?"
They definitely do not hack character creation. It's a combination of (free) trial accounts and stolen accounts they are "done" with. Once they've stripped down a character, auctioned/vendored everything, have transferred the goods and all of that, the account is just a billboard now. Goodbye level 80s, hello army of level one paladins marching in formation
"Why is Silvermoon called Silvermoon? Isn't that name a bit strange for Blood Elves? Why not Goldensun or something like that?"
Do remember that the elves that settled Silvermoon did so thousands of years ago, and they weren't all about the sun yet. They hadn't even taken the name the Blood Elves. They were barely even High Elves yet. Quel'Thelas was founded by Kaldorei exiles. As was mentioned by others in the comments, if the Blood Elves had founded Silvermoon, it probably would be called something else entirely. But Silvermoon makes perfect sense as a name from the people that actually named it.
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