I've been thinking about ways to make mages a bit more distinct from each other--right now, the only real distinguishing feature is the size of your dice pool and which skill you use (2 mages have access to the exact same spells, and if their skills are the same there's not much difference).
One talent I was thinking of was something like "Specialist Mage: choose one magical action you can use. Take a Boost die to all spells cast with this action."
Another possibility would be something to make a character who isn't a full mage, but has a knack for a specific action: something like choose a magical action. "Magical Knack: If when you spend a Story Point, you can use your ranks in Knowledge as if they were a magical skill for casting a spell with that action. You may not use any effects that are limited to a particular magical skill."
"Improved Magical Knack (requires Magical Knack): choose a magical skill (Arcana, Divine, Primal). You may use effects limited to this skill with your magical knack."