In one way I can say that it is working. But it's too dark to be seen. The thing is that the volume notifier, eg volume bar and speaker is not a part of the theme itself, but rather a part of the icon-theme. I was planning to create a variation of faenza supporting this but it hasn't materialized yet. But since you are working on an iconset you could very well create a set of light indicators. At the moment I can't recall the names of the icons, but if you browse through the hicolor theme I think you can find them. Short version, part of the icon-theme.