PS: I design my own greetings cards, using DTP software and graphics found online. I print them onto A4 glossy photo paper, folded in half to make A5 size cards. As you can't print onto the back of photo paper easily (not least because there's often a manufacturers watermark there), I print onto A5-sized sticky labels, which I then insert inside the cards.
Here's the front of a birthday card I designed for a cricket-mad 10-year-old earlier today
https://ibb.co/HnjFGL6
here's the middle
https://ibb.co/hgM1fZk
and here's the back
https://ibb.co/ThcfvmL
(There was no need to hunt online for a graphic there. It's my own beloved Chequers!)