Okay, you're asking about add-ons. And yes! You can add-on specific merchandise to create "custom tiers."
Once the campaign is over we are going to be using a service called PledgeManager. PledgeManager is a service that makes it easier to fulfill larger Kickstarters. They assist in exporting shipping data, help us track backer surveys at any time, allow you to update your address--and they even let you add on additional items to your original reward.
Read more about PledgeManager in this campaign backer update: https://www.kickstarter.com/projects/276501805/check-please-year-three/posts/2206176