I see, you mean consistency. Well, I call the theme "MetrialOS" for a reason. I wanted to put the aspects I liked together in a theme. Maybe I create a pure Material Design theme someday, but I really don't like the direction Google is taking regarding UI.The Icon of file types to be specific. If you can make them like the folder icon (border with semi transparent filling) that would be awesome. But if not then there's a really good set available here that you can use.
https://www.iconfinder.com/iconsets/file-extension-vol-1