Answer from the artist, Renne:
When I first started designing the deck, I knew I wanted to incorporate some tarot symbolism in the court elements, as traditional playing card symbology wouldn't translate well into owls. And thus began the first step of corresponding playing card suits to tarot suits. I went with:
Clubs to Wands
Hearts to Cups
Diamonds to Pentacles
Spades to Swords
Although I'm not an expert, I'd say these are the standard analogues when corresponding the suits. Nearly all of tarot's symbols are used in royalty as well - every king has a sword, a royal staff, a holy chalice. The only symbol that didn't quite fit was the pentacle, more often associated with religion than royalty. So for the diamonds, I had the owls hold a globus cruciger, making the cross portion into a bird's outspread wings. Each other suit got its respective symbol. One more thing - why do the Spades hold scimitars? I did some research, and found that scimitars were used on horseback - an ideal type of sword to be used in motion. Of course, an owl would always use their sword while in motion, so their weapon of choice became a scimitar.
The king and queen owls of each suit also received a halo instead of a crown, denoting their royalty. The jack, or knave, is the court card not considered royalty, so they don't have a halo.
The trees in the background have their own small meaning, as I made a personal association of the suits with seasons. So:
Clubs - Spring
Hearts - Summer
Diamonds - Fall
Spades - Winter
This is most apparent in the Spades cards, where the trees are mostly bare. Additionally, I used oak leaves for the Clubs cards, as in Germany, the Clubs suit is Acorns.
The Aces were special as well, as those cards in tarot represent new beginnings, and also endings. The seed that grows into a flower, or an egg hatching. The Ace of Clubs was a bit special, as the suit is associated with fire, so I made an owlish phoenix emerging anew from flame. The Ace of Spades was special as well, with it's own symbology as the death card. So that owl holds the skull of a bird, showing its role as a killer and its comfort with death.