I would definitely include a business card, and I know a lot of sellers write a coupon code on the back of the business card. I've received gifts before that were ordered from online, and I loved the work, but the maker didn't include a business card, so it took me a lot of work to figure out who exactly made the gift that I received! Danielle posted a great article in today's Etsy Success Reading list that you might want to check out - How to Deliver an Experience:
http://www.ducttapemarketing.com/blog/2011/04/26/how-to-deliver-an-experience/Also, I would also ask the buyer if they would like you to include a message to the recipient (if they haven't already made that clear to you). Congratulations on the sale!