With the payment gateway integration, currently the 'Card Type' dropdown has multiple types of card that may or may not be supported by the payment gateway being used.
We're currently using the Worldpay integration and, as I imagine is the case for most users using Worldpay, AMEX isn't supported. However when a customer clicks the payment link button to pay their invoice, the default selected in the Card Type box is AMEX.
Quite a few of our customers have filled out their AMEX details and clicked to pay then to be told the card isn't supported.
It would be useful if you could choose which card types to have in the drop down list on the payment page to stop this happening.