Done Nusa Penida, Bromo Tengger Semeru National Park and Ubud too when traveling in Indonesia in September and they were all 3 highlights in my trip.

Yogyakarta with the temple complexes Prambanan en Borobudur close by are also highlights of Indonesia.

btw, check out my post about climbing the Semeru vulcano. Bromo and Ijen are following in part 2:
https://steemit.com/indonesia/@pieter87/climbing-mount-semeru-indonesia