The images we have so far are for the Nexus 5, 7 (both WiFi models), 9, and 10. There's no Nexus 6 image yet. Devices like the Nexus 4 that aren't getting an OTA just yet are also still waiting on the system image. Binaries are also up for all the devices with factory images, save for the Nexus 9, which has the drivers on a separate system partition already.
Head to: https://developers.google.com/android/nexus/images
Source: http://www.androidpolice.com/2014/1...re-live-for-nexus-5-7-2012-and-2013-9-and-10/