Permanent Death with Revival Tomes would be very interesting. Depending on how we'd obtain it, it'd be cool to know that we risk our character's life, but there's always a way to cheat death, if only once.

Would there be any type of resurrection spells, too? there would be limitations, of course, but in regards to that, how should it work?

We should also come up with different spell categories as well, if you haven't already. Are you planning to have a set list that people can learn from, or would it be a freeform system ?