This is probably a mistaken request on the part of your cardroom. It's very likely that you won't have to send in any images of your card.
If you have not deposited with a credit card but your site nevertheless asks you to send copies of it, then this is most often just a small error on their part. Customer support agents typically follow a standard script, which is optimized for the majority of their customers who tend to make credit card deposits. Simply get in touch with support and explain your situation, and they will likely waive this requirement in your case.