The European Space Agency (ESA) has a
a site for festive e-greetings. There is a selection of space-related images and at the top of the frame a rolling succession of festive greetings in numerous languages. (I don't even recognize a lot of them!) What you send is in postcard format.
If you have a friend or relative of any age who's a space fan, this might be fun for them.
You choose the picture & write your message. ESA emails you a link & you use that to send the card. (Stops people using the site for anonymous messages.) Your recipiient gets the picture surrounded by the red background and succession of seasonal greetings. They click to see the message on the other side, and there's an option to download it as a PDF.