Moments after pushing Android 5.1.1 “LMY48I” to AOSP, Google went ahead and made factory images of the new build available as well. We are currently seeing factory images for the Nexus 4, Nexus 5, Nexus 6, Nexus 7 (2013) WiFi, Nexus 9 WiFi and LTE, and Nexus 10.
Over-the-air (OTA) updates will likely start rolling out tonight, so stay tuned for those files. In the mean time, you can grab the factory images for your devices at the link below. To flash a factory image to a Nexus device, hit up this link.