I figured it out, I think to customize you need plus store to modify the checkout.liquid template, but it is going to be deprecated as well. Hopefully there is a new way of customize them...  

Hello everyone, We're currently developing a payment app for Shopify. During checkout, when customers view the list of payment methods, they only see plain text names. We aim to enhance this by adding logos and dynamic text, such as earn $xx.x cashba...