I've been away from the community for a few months, but was very much reminded of Guns of Icarus when I got my hands on a copy of Last Exile.
The large airship battle scenes are incredibly epic--too epic for the wood-and-balloon combat context of the current age of GoI. It did make me think about those giant rusted relics on Dunes and the metropolitan ruins of Labyrinth, as well as the enormous ribs on Duel. The initial combat is actually ships opening up their side armor and using steam-powered muskets to fight American Revolution-era line-against-line battles. It's an interesting intersection of chivalry and, in some cases, victory by exploitation of those practices.
I'm unaware of any substantial existing backstory to the current state of affairs in the GoI universe. If nothing else, I wanted to share a great series in the same vein as this game and serve it up as idea fodder.