CyanogenMod has always been on the forefront of ROM customization, and its newest release, CyanogenMod 12, is no exception. In the newest nightlies, they have included an updated version of their Theme Engine, which allows you to effortlessly change the way your entire system looks.
Unfortunately, installing the Theme Engine cannot be done via an APK or TWRP flash. The only way to use it is to flash the newest nightly release, or another custom ROM that has the feature baked in. If you do decide to use the nightly or a custom ROM, know that they are not official releases by OnePlus One, so… more
Sig Nordal 