You Should Be Using This Free CM 12 Theme: Elixium UI

Theme Engine is somewhat a new addition to the CM 12 nightlies. Due to Lollipop being a complete overhaul, the Play Store lacks good CM 12 themes.

At the moment paid CM 12 themes aren't worth it

I loved using CM 11 themes. I had even purchased a few CM 11 themes. My favorite was Veu by Arz Bhatia. He has insured that Veu will be coming to CM 12 but the date hasn't been announced. At the time of writing this, the options are quite limited when it comes to getting a good CM 12 theme. The ones which are paid are not worth it. They offer the same thing as some of the free ones do. For this reason I've picked Elixium UI out of the few limited options.

Elixium UI offers more than a paid theme

Elixium UI is simple. It has a unified look across all the OS. Main color of Elixium is beautiful. This color will be seen all across the OS if you use this. Its a lighter shade of black. It looks stellar, I couldn't have asked for a better color.

Elixium UI, offers quite a lot of customization. Although it's free the developer hasn't left anything out. It comes with its own custom ringtone, alarm tone, notification tone, wallpaper and boot animation. The theme also offers a beautiful set of fonts. I've noticed two different fonts being used throughout, a roboto condensed and a light helvetica? They look gorgeous. They blend in amazingly with the rest of the theme.

Keyboard looks great

Verdict

There isn't anything to hate when it comes to Elixium UI since it's free and it's better than almost every paid option out there. There's also a separate app you can buy to support the development of the theme, which I encourage you do.
Download:
Elixium UI free 
Elixium UI donate