A recurring element in Oceanic mythology are shapeshifters. A wereshark or werebird following Oceanic rather than Western rules and characteristics could be a nice surprise for your players.
Menehune and their mythic buildings could make for a small dungeoncrawl, and you could throw in a lot of related crackpot theories like that of the continent Mu.
Nanakia (woman-stealing jungle goblins) and Tutumaiaro (ugly gnomes who beachcomb and haul treasure with nets at night) are also too weird to ignore.
If you want to play with Tikis, you could play around with Porotai - double-faced stone spirits who can turn invisible.