Current interface of Haruna is not visually pleasing; to put it in nicely. You can make a theme system, so others can make theme for it easily. You can start with looking into Bomi player themes. Bomi skins are written in qml.
Bomi player had the most beautiful skins. But it’s a shame the project is abandoned, and those beauties are rotting in an obscure repo.
Screenshot for reference.