You can use any artwork from the EarthSea Gallery as an eCard image. Browse the artworks in the either our Prints or Paintings sections and follow the 'eCard' link under each artwork to get started.
From the Wikipedia eCard page:
An E-card is an electronic postcard or greeting card, sent by means of the Internet, usually through e-mail.
A sender of an e-card would select a pre-written card style with image and message, and would add their own personal message, and specify the recipient's e-mail address. On sending the card, the recipient would receive an e-mail with a link to the e-card provider's webpage, and this link would go to the e-card as a webpage, with the sender's personal message and card. Note that the actual card is not usually sent through the e-mail, but only a link to the card hosted at the e-card provider's website.