This post went quiet last year but I'm going to pop some ideas in anyway. XD
Horror movies (Everything from Freddy to Xenomorphs c: )
Gaia Evolving Items
Mother, Maiden and Crone (Would only be a trio unless others were made to compliment but could be AMAZING)
Superstitions (Black cat, broken mirror, salt over the shoulder)
Pirate/Rogue
Plant based (Creeping vine, willow tree, moss)
Comic books (Not just like Batman and Spiderman but comics like Witchblade, Fathom and Tank Girl)
7 Deadly Sins/Heavenly Virtues (Those may have already been done)
Good Dreams/Nightmares
Plague/Healing (Plague could be Kimeti who spread disease and illness while Healing Kimeti can cure said ailments, could be a rivalry)
I'll stop now. xd
Also I love the Herb, Perfume, and Horn ideas. <3~