These files range from 440MB to 465MB and will require fastboot set up to install. The major change to the OS can be found in the dialer app, with new color accents and a card-based process for speed dialing. Other improvements include one related to CPU usage and the Nexus 5 camera. A previous update to Skype triggers heavy CPU usage when the camera app on the Nexus 5 is opened. This leads to a severe drain on the battery, and the inability of the user to actually use the snapper.
Those who would rather wait for the OTA update can choose to do so, as long as their patience holds out. Otherwise, click on the sourcelink if you want to use the new factory images.
source: FactoryImages via AndroidCentral