I assume there are guards running about and warning the people while others muster at the walls, as well as bells and the famous warhorns. I believe it was Peik that said it first, but if there's anybody who's been around with Gcold and I long enough, they'll know the ironclads are carrying Kamal invaders. Imagine sentient frost-trolls clad in armor and your expectations won't fall far.
These ships are more like proto-ironclads. The twelve ships we see coming to Windhelm are only part of their fleet. Because the White River is shallower and narrower than the Sea of Ghosts, only lighter vessels can squeeze through. There might be true ironclads somewhere else, but the assault ships are built from wooden foundations, with metal armor fused on. They have some sort of magical self-propulsion, but still relies on sails frequently. These things have firing ports occupied by magical weapons, kind of like enlarged version of the projectile shooting crystals in Skyrim dungeons.
Kamal themselves are around 2.5 meter/8'6 tall, covered head to toe in deep blue metal armor. The body armor is made from similar alloy as their ships. They do not show an inch of their skin/fur/hide, or whatever is underneath. They are also as intelligent as everyone else on Tamriel.
I might write an in-universe article explaining these guys.
Also, are there bells in Windhelm to sound the alarm, or are the guards in charge of warning the people? I know Dough-Boy is in charge of alerting the members of the company, but what about the rest of the citizens?
The scene was inspired by
Skyrim live action trailer. It's a combination of evacuation alert and call to arms. I imagine Windhelm having a well developed early warning system, from its days as the rebellion capital and danger of dragon attacks.
The Windhelm jarl is a dude called Lodvemar. He was hand picked by Thur for this position. Ulfric was strangely murdered after the civil war, and the next likely successor; Brunwulf Free-Winter, went missing after speaking out against Dovahkiin's tyranny.
Hey, just giving you a guy's a heads up I'm heading to the hospital tonight. I don't know if it's going to be a multi-day thing, but I'll let you know as soon as I can.
Get well soon buddy.