The Pass Designer and CherryPie allow you to select which Barcode Format you wish you use. Please note that this is not a constraint of PassKit or the Pass Designer, this is a constraint placed by Apple in the Wallet App.
If future Passbook release supports other Barcode formats, PassKit will of course support.
The barcodes that Apple Passbook currently supports are:
Code128 (iOS9 +)
If you urgently need to use another type of Barcode (for example, if your existing scanning equipment only works with a certain format) you may consider uploading an image of a barcode into the Pass itself (eg as a Strip Image in a Event Ticket). Of course this means you will not be able to have another image on the pass. Refer to Pass Constraints for more information.
If you would like Apple to consider other Barcode formats in Passbook we suggest you request an enhancement direct to Apple. Please visit https://developer.apple.com/bugreporter/