I would really like some sort of “participation in design” add-ons/tiers.
Give us the chance to design something in the game, maybe an item or a little random mini quest. Or give us the possibility to transfer our faces to the game to model for a certain NPC. I don’t mean things that would drastically change the game, just some small personal input. And Warhorse would have the last word on it anyway so that shouldn’t be a big issue.
Many other kickstarter games did the same with great success (Pillars of Eternity, Divinity Original Sin, …).