That's the big thing I see missing here. "Having it sent" is the goal of the game. Otherwise I might as well snap a personal photo and send it with Postino (which is how I am doing things now - and unscientific sampling shows that is much more likely to stay on somebody's fridge long after the event is past).
Still, wrapping paper has some potential, especially if they offer good quality paper, which Hallmark/Walmart/whatever don't seem to carry much.
Possible variant: Accept a picture/image of a handwritten message, and apply it (cleanly) to the card / piece to be mailed.
EDIT: I'm thinking of e.g. an image from a cell phone, if you can get sufficient quality. Not something that becomes significant effort for the user. Bonus points if, or necessary that it looks (fairly well) handwritten.
* Enter in a list of all those family members I'm obliged to send birthday and Christmas cards to, including some basic demographic info
* Upload an image of my handwriting
* I'm reminded at the appropriate times to pick from a filtered selection of cards and enter a personalised message
* Printed & sent (bonus points: handwriting looks real)
Someone build this please!