The Pillar Mountains, Evergrind City, Mt. Bloom, Tai Ming, Santa Fae, Pumpkin Woods and the Flying Fortress are the only places there teleport plates are present as far as I can remember.
While there isn't one in Seasonne at the moment, I'd at least like to see one, it being the only area before a dungeon without one. Walking over there from Evergrind while you haven't unlocked Santa Fae yet is a bit of an annoying trek.