The video above was actually released by Cyanogen Mod back in November, but what it demonstrates is the all new Themes app which will be available in Cyanogen Mod 12. This is an improvement to the Theme Chooser app in CM11. It includes a Material theme and allows you to customize every part of your Rom. You can change your font, bootanimation, and there is even support for custom icons. The themes app allows you to browse themes that are available which will work with CM12 and install them directly from the app. You can expect a ton of new themes to be hitting the app. Cyanogen has also announced a new Themes Studio which makes it super easy for theme developers to develop themes for CM12. Cyanogen has also launched a contest for themers so I'm sure there will be lots of different options when this finally makes its way over to the official builds of CM12 later this year.