I'm just going to
tell you what I do for my desktop. What I do for my desktop is this: on the first of each month I download the respective month's image from my ancient website of Les Très Riches Heures du Duc de Berry, which is a large corpus of illustrations making the pinnacle of late medieval artwork. It was mostly a prayer book with illustrations of bible scenes, but it also included a calender! Hence, this is the present image I have for my background:
