I like making my own cards, and find simple naif designs with scraps of fabric and free motion stitching quite satisfying to make. My daugter has just moved into a new flat, and this is what I've made.
I used some blackout curtain lining fabric as the background as it is solid enough to stitch on without a hoop. I'm not very good at controlling the stitching, but I say that the imperfections just add to the charm!
I use a Pilot Frixion pen to draw on the designs, then just use a warm iron to remove the marks. I know there is some debate about whether the marks really disappear, but it is quick and fine for a project like this.