Whether your familiar with the hit anime series Saint Seiya, mostly popular in Japan, Europe, and Latin Americas, Masami Kurumada's talent and art style to create distinct armor sets is unrivaled. This is a huge untapped resource of inspiration for Blizzard I feel, to create new armor sets going forward. Kurumada created unique armor sets for more than 200 characters, inspired not only by astrology, but Greek myth in its entirety. Here are some examples.
Aries, The Ram and Taurus, The Bull. I could see Tauren and Highmountain Paladins rocking similar armor sets.
Gemini, The Twins. Explore humanity and The Light's duality.
Cancer, rotten to the core and evil. Warlocks, anyone?
Leo, heart of a lion. Heart of a Warrior?
Virgo, The Virgin, pure and transcendent. Priest, anyone?
Libra, balanced, and an arsenal of Chinese weapons. Perfect for The Monk.
Scorpio. Cunning, swift, bloodthirsty and potentially merciful. The Rogue.
The Centaur, half-man, half-horse. The bowman. Obviously, The Hunter.
Capricorn, a skilled swordsman ready to impale any evildoer, just like a true Warrior.
Aquarius, commander of ice and water. Mage or shaman, take your pick.
Pisces, I could see this as a Shaman set.
Death Knights, look no further. For the Blood Elf Death Knights, I bring you the Death Fairy.
If we had a Bard class? The Lyra.
Perseus, rocking the legendary shield of Medusa. A Warrior with a shield that turns the targets to stone for 4 seconds sounds awesome.
The Dragon, another potential Monk set.
Andromeda, pure and sacrificial for the greater good. Chains with life of their own, or moved by The Light? A feminine Priest armor set.
The Cygnus, graceful and right at home in the ice. A mage cloth set.
Lastly, The Pegasus. This set looks like it could look good on a Warrior.
Obviously I'm not saying Blizzard should straight up rip off aesthetics of a trademarked anime, but The Horoscope and Greek Myth cannot be trademarked, and they could easily take inspiration from there as Kurumada did for his armor sets.