Nexus 5 is an amazing phone, and you get regular updates on it, but you can have so much more fun with it. For instance, you can download and install the latest AOKP KitKat ROM on it. Installation is straight forward and simple.
1. If coming from another ROM or another major AOKP version, wipe data in recovery
2. Make sure you’re using the latest CWM or TWRP (recommended).
3. Download the ROM from here and flash ROM by placing it in root folder and then going into recovery.
4. Flash Google Apps (GAPPS). Download it from here and flash it in recovery.
That is it. You can successfully downloaded and install AOKP on your Nexus 5 Android phone.