Being the Lock King means you have to have a UI befitting of your demonic power, and what better one than a UI based on Diablo's?
Near the end of my "adventure" on retail, I used roth_UI and roth_Diablo to achieve this.. but haven't found an older version. There's supposedly a modified one on the Feenix forums that works in Vanilla, but rather look at other options before settling on the first available.
Anyone know of other addons that can simulate this look?