Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
You can only create the kinds of passes that PassSource offers. If you want to add a new type, such as your VISA card, you'll need to become a paying member of the site and get access to their API.

That said, I'm not sure Passbook was meant for debit cards. There's nothing to scan on the real card that corresponds to your bank account - unless you want to try squeezing your phone into the magnetic swipe reader...
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.