Download and install Cyanogen 12 Black Azure Theme. This is the best choice for all black themes freak. It will change your device look totally. Once this theme is installed you will have a fresh new phone, with an interface that will look awesome.
CyanogenMod 12 is the best Custom ROM you can find around. It is based on official Android 5.0 Lollipop and has all this features. Since it is developed by developers who has nothing to do with the manufacture, CM12 is developed as a ROM optimized for best performance and free of bloatware or any other pre-installed manufacture app.
CyanogenMod 12 has also its own characteristic user interface but you can change it anytime if you find a compatible theme. To install Black Azure Theme you need to install before CM12 Theme Engine. This theme is tested in many devices and all users have been satisfied with it.
Before applying this theme you need to go back to the stock theme. Then to install the new one.The theme includes change of the icons also. So you phone will look like you have installed the CM12 ROM. simply download the apk file from here, and then tap on it to install. Choose Holo White or Blue in Google Keyboard and then reboot once or twice if needed to theme to set.