Alright, so mine was a process to figure out and I'll definitely update it as the story progresses and I get more experience. But at the moment, it's this:
Our dual protagonists front and off-center. Both facing the directions they travel at the end of their respective prologues. Omari heading West while Xiaolian heads East. Behind them is where they're coming from. Behind Omari are Egyptian Hieroglyphs since he's coming from Egypt (with some treasure too), while Behind Xiaolian is a Chinese painting, coming from their homeland. The backgrounds also have the opposite gradient since the protagonists will end up meeting shortly after. In Omari's hands are playing cards with the Ace of Hearts in hand purely because I like it best and wanted to differentiate from the Ace of Spades which I would say is the most common card seen. Their poses are opposite as well with Omari turning his back to the audience while Xiaolian has theirs open.
Surrounding both protagonists are their unique abilities, their Summons (which are a universal ability where Passion, Personality or Potential manifest Power). Omari's Summon is invoking a wind at his back while Xiaolian's invoking her clan's heritage, the Wu Xing Dragons. Specifically the water dragon Shui Long boosted by Metal.
In the middle is a checkerboard pattern. This has a double meaning. Both are headed towards a city with a mile-high prize that features a checkerboard pattern at the center of the city. More importantly, it's symbolic of the importance and prevalence of games throughout the series. Many games are played on a checkerboard, so the black and white pattern invokes that. Also a subtlety on morality and decisions that may or may-not break things down into black-and-white.
In short, the cover is meant to give a general look into the series as a whole: The world-wide journey, the importance of games and the power awakening in our casts.