Thanks for posting your query.
I believe that you are interested in knowing the back side of the printable version of the card.
In that case, the back side can't be customized.
For your reference, below is a sample URL of the card sent, where a user gets an option to print the card.http://www.123greetings.com/send/view/0 ... 0508826827
Kindly let us know, in case you have any further queries.