Selling Greeting Cards Online With a Subscription

I still want to sell my art as ecards, online. Today I found someone with a good plan, selling the cards with a paid membership to the site. Ojolie offers a free account, to send the ecards she offers without charge. But, I think, I would rather make the ecards a subscriber only thing. Art online is just too easy to rip off. At least I could get a year’s subscription before giving access to the art. Of course, I still don’t know what software to use. Something like a catalogue, but then it needs to send a png file, or pdf. I think I would include envelopes too, a bonus should people print the cards. So much to consider when you start to think about all the details.