Tossing out a 0.02
Like OZ said, the question of Classification By Energy/Source vs Classification by Effect is an important one if you are planning to include several different types. Especially with Ritual Magic, as advanced techniques of most any of the others (but especially thaumaturgy, summoning, and necormancy) could potentially cross into ritual areas. It raises the question Is a ritual about the about the structure (ie symbols, words etc) or is it tapping some specific (or maybe just universal) power or being?
Other Questions to ask:
-What are magic objects/artifacts considered?
-Is there magical healing/medical of any kind?
-Does Blood Magic make an appearance, or is blood used in other types (ritual, necro, evocation). Blood magic is one of the few magic types that seems to show up in every world, to one degree or another.
-Is Sacrifice (human or otherwise) part of any types (ritual, necro, summoning via trade, etc)
-Are illusions purely sensory? would mental control count, or would it be Thaumaturgy
-What are the limits? What, if anything, is considered impossible across all types? (ie resurrection, time travel, transmutation, teleportation, etc)
-Can you travel to the Spirit World, or does everything come one way? Do things fromt eh spirit world have bodies, or make them?
-Is evocation for base elements still tapping another location/plane? ie fireball via Elemental plane of Fire or a portal to a volcano/star.