Main thing is that default ctb and taiko are very specific in setting and/or characters, with ctb being fruit/food based and taiko being drums and probably some japanese lore I don't know.
Meanwhile, you can tell by the mania default skin how it tries to be reminiscent of BMS or whatever it was called, no specific theming in setting or characters.
If it were up to me, I'd keep it open ended/vanilla as is, though make it apparent its inspired. As well, I'm not a fan of difficulty names that call the player something unironically (so as slowpoke says, "experienced" or "novice" is not something I want to be called by the map I'm about to play and possibly do terribly on):
- Basic (Easy)
- Intermediate (Normal)
- Advanced (Hard)
- Challenge (Insane)
- Extreme (Expert)
- Master/Legendary (Expert+)
Now I do see in the difficulty naming section that "Extreme" is widely accepted for expert+, but hey I didn't need to like it.