You can add a card that is not listed in Stocard as "Other card".
There will be a card symbol as default logo for all your custom cards. You can change this icon by opening the card and then by clicking on "Edit". Then you have the option to "Add Icon" (which could be, for example, the front picture of your card or a picture of the card provider downloaded from the internet).
Tip: You are more than welcome to suggest new cards to be listed in Stocard. Just drop us a note on firstname.lastname@example.org.