Any plans to send gifs as well? (gifpop.io is good inspiration)
However, If I sent my grandma a postcard that moved, she'd probably collapse :p
I'm surprised that none of the postcard bots (yours included) have targeted the Christmas/holiday card or wedding gift thank you market. None of them seem to offer bulk discounts or options for uploading a csv or better yet integration with iOS or Gmail contacts.
Average number of wedding guests in America is 150, iirc.