It looks like your question has largely been answered but, as I design my own Christmas cards, I'll offer you an alternative technique. That's to use a desktop publishing program. See my post here for a great freebie:
https://www.theanswerbank.co.uk/Technology/Question1580041.html
(Note that, after clicking the 'Download' button, you should select 'Softpedia Mirror')
I design my cards to print out onto A4 photo paper, so that they'll fold to A5 size (and thus fit nicely into C5 envelopes, available from pound shops, etc). Since you can't print onto the backs of most brands of photo paper, I print onto A5 labels (with two labels on an A4 sheet) and stick those inside the cards:
https://www.ryman.co.uk/q-connect-multi-purpose-label-2-a4-sheet-pack-of-100-white
I get my graphics from Google Images.
Here's the outside of this year's card. (It obviously needs to be folded down the middle). It only took me a few minutes to knock it up:
https://img15.hostingpics.net/pics/6313272017card.jpg
(The inside simply reads " . . . our pet human, Chris")