Being a Tarot reader, I am heavy into symbolism. So here goes...
The web of pink roses, at least that's what it looks like, of course would mean all the intrigue and danger.
Elizabeth's picture at her solar plexis area, the root of fear and jealousy, which Elizabeth was to Mary and vice versa.
White horse with Red Rose, the fact that they were both excellant riders and maybe the fact that Elizabeth wanted Leicester to marry Mary and he was Master of Horse.
The Lion in Mary's hand, the english Tudor lion, her greediness for the English throne and lions are the main symbol for royalty.
The lute with the sword with it, could symbolize how Mary's enjoyments and voice was stifled during her imprisonment in England.
The knight aiming for the mermaid, could indicate Mary's affects on men (siren type) and how they betrayed her.
The suit of armor without the top of it's head to me signifies her imprisonment, the plots that surrounded her and the indecision by Elizabeth of what to do with Mary.
Also, look at how her left hand is in a red glove, and part of her arm is blacked out. Wasn't red the color for a Catholic martyr? Was Mary left handed, this could mean many things if she were. The implications over the Casket letters and her passion for her faith and her own royalty, the blood she shed. One half of her is white and one half is red and black. The Tudor rose colors red and white. And the fact that she was one of the first to wear white to her wedding and red at her beheading.
Of course it is all opinion, but fun to decifer! Seem to be many more images to ponder but the picture is not real clear once you print it. The finer details get lost. Thanks for the challenge.
Tudor