Most of the art used is public domain, which has limited the number of deities we have an option to work on (since public domain work is more often "the work you have" rather than "the work you want"). One piece in particular, the Brigid Prayer Card, was done by Christina Marvel, and I think it's amazing. I cannot describe how happy I am that she let us use it for this project.
Piecing together the prayers was the hardest part (still is). I wasn't sure how to set up the cards so that they would work for a wide variety of people. The prayers I've settled on deal with certain aspects of the deities, rather than being general prayers of praise to the deities (which I write a lot more of in general). It's been really nice, though, to get to work with these deities and read their lore.
The prayer side of Apollo's card was the one that first made me realize that we might have a pretty quality idea here. I spent a lot of time reflecting on the roles I could call out in the prayer, and settled on creating a "Prayer for Clear Sight" for the back of the card.
Pan's prayer turned out to be a bit more lusty than I expected, though I suppose in hindsight that makes some good sense. Odin's prayer went through two complete revisions.
I'm still working on prayers for a few of the cards, but they should be done in time for us to send the first run off to print. We're waiting on our first draft of the cards to come in before we order the full set (Oðin is on order right now).
The cards are going to be the same size as baseball cards (about 3.5" x 2.5"). I'm only sort of joking when I talk about doing "Archdruidic Rookie Cards" after this.