Thank you for the encouraging replies, everybody
I made couple of test versions and they turned out nicely! Used bit of tape on edges to make sure the image and cardboard stay together, and to smooth down the otherwise sharp edges. Too bad I don’t have white washi-tape. It would have made nice frame edges, I think.
Not the fanciest cards around here, but should be fine for the selected profiles that are okay with handmades and these themes I got.
And while I was looking for cardboard (ended up using the ones that came with stamp orders… I knew I was saving those for something!) I found also another calendar, the one from 2019 (and that one has really nice nature views)! The 2018 is probably around here somewhere too, because why to throw away things when you can just stuck them into storage somewhere. So I got now lot to use my time with