Recently I've been working on a UI for credit-card payments. As part of this we needed some credit-card icons to show the card type as the user types in the number to the input field.
In looking for existing iconography I either couldn't find exactly what I was looking for, or the license terms were unknown. In the end I built up a small set of icons using a mix of Sketch and InkScape and provided them as svg on github.
You can see a preview of all the current icons here.
The repository is at https://github.com/muffinresearch/payment-icons (MPL 2.0).
If you want to contribute updates or improvements ti these icons, please feel free to submit a pull request with any changes.
If you have new icons you want to be included then please follow the examples given and add your icon for each of the existing styles and make a pull request on the github repo.