Graphics Data
Tinke
Tinke is a great tool for extracting files, but also doubles as a great tool for handling 2d art assets. While many of such files need to be decrypted and decompressed to be used with it, after doing this they can be saved to .png and such with Tinke.
Apicula
Apicula is a great tool for anything model related in many Nintendo DS games. Phantasy Star 0 uses Nintendo's formats and so this can actually convert models and bone-based animations for use in a program such as Blender. It also has a great preview feature. A tutorial on its usage can be found on its main Github page.