Movie room; it isn't too difficult to come up with 48 to 72 hours of steampunk video. If you run short, you can pad it out with TV episodes.
Food. For one of my (non-steampunk) events, I was contacted by a couple of young entrepreneurs who wanted to publicize their new venture by providing an assortment of unusual cupcakes. You could have a tea table or even room at your event depending on the scale.
