Spells: I agree with the guy above about portals. I like to play Wizard/Mage because they have those unique spells that can be really helpful outside the battle. Portals is one of them. Maybe some Water/Food conjuration also.
Animation: It would be nice each class to have one or two specific animation. The mage could have something like reading the spellbook and moving the hand like if were practicing or maybe doing some prestidigitation (DnD)(playing with some fire, levitating small objects, etc). Just for fun.
Armor: It would be nice every class to have some specific vests or even a Tier (like WoW used to have). Some robe or staff that can only be used by a powerful Mage (or like for other classes a robe/staff that can only be used by a holy Priest).
Mount: I like the idea of classes having unique mounts too. Maybe a Mage could have some arcane creature or something magic that floats.