From the update:
Here is list of the first Add-Ons available. More Add-Ons will be revealed as we unlock new themes.
Upgrade your pledge and help us reach the next stretch goal!
To get additional accessories just increase your pledge according to the price list shown in the Add-Ons list. At the end of the Kickstarter you will be able to select among all the unlocked upgrades up to the additional amount pledged.