Bah, they might be right not to show anything for now.

Following the Project Zomboid developpement (which is in alpha), you can't imagine the number of dumb fucks buying it and complaining that it's bugged and busting the dev's balls because they didn't understand what Alpha means (when it's written in big red bold letters on the purchase page)

Kickstarter and crowdfunded websites have strict policy and "investigation" system to know if a project is a vaporware or a scam. Not showing any gameplay and holding back might as well be a "marketing" choice ;p