The one on the picture is a model, but there are cannons you can use to defend your village in PvP (RvR as the call it). There are also quests for usage of those cannons.
And may be they were smart enough to make you control a a steam tank. We'll see.
As for the classes or your character:
Order->Dwarves->Engineer(marksman)
Order->Dwarves->Ironbreaker(warrior)
Order->Dwarves->Runepriest
Order->Empire(humans)->Bright Wizard
Order->Empire(humans)->Witch Hunter
Order->Empire(humans)->Warrior priest(healer/dps)
Order->High Elves->Swordmaster
Order->High Elves->Archmage
Order->High Elves->Shadow Warrior(rogue)
Order->High Elves->White Lion(hunter)
Destruction->Greenskins->Goblins->Squid Herder
Destruction->Greenskins->Goblins->Shaman
Destruction->Greenskins->Orcs->Black Orc(warrior)
Destruction->Chaos->Chosen(dark magic)
Destruction->Chaos->Magus(arcane magic)
Destruction->Chaos->Zealot(shaman)
Destruction->Chaos->Marauder
Destruction->Dark Elves->Witch Elf(rogue)
Destruction->Dark Elves->Sorceress(dark magic)
Destruction->Dark Elves->Disciple of Khaine(warrior)
WAAAGH!