Of course, MissNine, I'd love to offer up a few explanations.
To me the Coins / Pentacles / Disks suit is indeed "earthy"... which means I associate the courts with a pragmatic, down-to-earth, traditional way of thinking. More "no-nonsense", and related to palpable things (the body, wealth) rather than a character who's passionate (Wands), emotional (Cups) or intellectual (Swords). I associate Coins with "wealth" - not only financial, but also in regards to health. And, as mentioned above, tradition plays a big role here.
Thus, the King is an accountant and an ISTJ because of his Coins-Earth association. To me he's the most materialistic of the Court cards - which means he's great with numbers and business, and he appreciates tradition, rules, standards by which to judge the situation... He's basically a stereotypical father providing for his family - because, after all, "family" is one of the greatest things in the life of those with deep respect for tradition. He'll be awful in regards to his teen children's passions one day, however. He'll probably grow to be the father asking his "punk" son what he intends to do with his life - because obviously, he can't strum that guitar forever! Haha, yeah I like to picture my chosen "courts" in random scenarios sometimes
The Queen and the Princess (Page) of coins were chosen together. I knew that I needed a typical, motherly "housewife" in the Coins suit, and at first I thought of giving that role to the Queen - to have her be the perfect wife to the traditional "King" husband. Both ESFJ and ISFJ could work well as "housewives", but again, to me the Coins suit is about money, but also health. So with the King being related to money matters, it seemed appropriate to give health/body matters to the Queen... Or at least that made sense to me at the time
). Both the Queen and the Princess are nurturing and down to earth, they're both in roles traditionally assigned to women, but the Queen cares for others in a more professional manner - she's not just a mother; she's a nurse... A healer, but a professional - as opposed to the "housewife" who will make it her life's mission to love and care for her children, but who does so by following tradition rather than by choosing a specific job. One is an active "choice" while the other just follows the natural order of things. In other words, my Queen is a more "evolved" nurturer, so to speak.
And the Prince (Knight)... We have "Fire" (knight), under the rule of "Earth" (Coins). He's not fast and passionate, like the Prince of Wands (the Athlete, Fire-Fire); but he does get the job done, since he's got ambition and loyalty lying under the "earthy" exterior. He's aggressive, but only when he has to be (unlike the Wands Prince who's an explosion waiting to happen). He's organized, cares about the rules (like the "King" father), and like the rest of his "Coins" fellows, he will defend things that are traditionally deemed invaluable: his country, in the case of the Soldier. "Country" / "Nation" doesn't mean much to me, personally, but to those with a traditional view on things, it's a great source of pride and something that's worth risking your life to defend. So... Soldier Prince of Coins.
I'll try to write explanations on all of my chosen Court Cards in due time, and hopefully those will sound a bit better, but for now... That's how I see these characters, in these roles. I hope this helped!