In the Mary-el Tarot, Queens are related to 13, winter, Aquarius, Angel (or winged man), liquid, Water, Cups, Heart, Humanity, III The Empress, XIII Death, Vav, 3-Binah (understanding), and the Black Horse (from the Chariot).
In addition, “Each queen has her own gem that speaks to her character.” (White, Landscapes of the Abyss)
Queen of Wands = Obsidian
Queen of Swords = Emerald?
Queen of Cups = Pearl
Queen of Disks = Diamond
From my own observations, the queens appear to be divided into two sets of ‘sister queens’. I first noticed the similarities in the Queen of Disks and the Queen of Swords. Both have only their left eyes visible. The Queen of Disks’ nose and lip are pierced by the spiraling hair-like growth that branches out of her head. Likewise, the Queen of Swords has twisting branches growing in and around her nose and mouth.
In comparison, the two other queens show their entire faces. Each has an animal at her chest and wears a rounded headdress. In the middle of her forehead, the Queen of Wands has a piece of obsidian which is formed in a fiery volcano—her element. The Queen of Cups has a lotus at the center of her forehead, which grows in her element, water.
Each of the courts seems to have one suit that stands out from the others in some way. The nearly invisible Queen of Swords is most unlike the other queens in that she is literally made of her element, air. She is also the queen where I am least certain which gem she is characterized by, though I infer from the green eye (a recurring motif in the deck) that it is the emerald. Notably, emerald is said to have healing powers for the eyes, mental illness, and neurological disorders, as well as strengthening the memory and intelligence. (http://www.all-gem-stones.com/se/emerald.html)