Yes, for the Android version of Stocard it is indeed possible to also add your passes (e.g. boarding passes or event tickets) to your card list in Stocard. In order to add one of your passes to Stocard, simply open the particular "pkpass" file (usually you will receive this file as an email attachment) and select Stocard as the app that should be used to open this file. Your passes will be displayed in a separate section right below your loyalty cards.
In case you are using Stocard on an iPhone, find out how to add your cards to the Apple Wallet here:
Can I add my cards in Stocard to Apple Wallet?