I can't really imagine going non-Seren (been on the brink of going Spiritsinger a few times, though).

Shadowdancer might be interesting, but if I had to switch I'd try something new. Bards are generally fun, but apart from the Spiritsingers they seem to be mostly inactive guilds. Druids/mages are not for me, nor are warriors my character's style.

I'd probably go Nihilist because of the cool culture stuff Magnagora has and the general fun of the Demon Lords. I hear they're pretty nice.