I've been mostly happy with how the Dwarves and Elves have turned out, but I felt like differentiating the other half-nymph species has been much trickier. They should all share characteristics, but still need something to differentiate them. Adam suggested making a base half-nymph template, and then giving each of them a specific package in addition to that. That felt like a simple and elegant solution to me, so I want to give that a try.
They should all share some degree of magical power, so that part's easy. I was reading through Power-Ups 3: Talents, and that struck me as the best way to differentiate them. Maybe each will have one augmented attribute, in addition to an ancestral talent. This could also be extended to cultural talents for my other nations. That'd be an easy way to add some character to humans from different regions. I had been targeting 35 points for the templates, and I may continue using that value.
The keys at this point are to finish character templates, and to finish writing my magic rules. I think once I finish those two things I have enough other stuff either built out, or planned in my head, to be able to start a campaign in this world (which ultimately, is the goal).
I should probably add something here.