A few months back Google released the current factory (stock) image of Android 4.4.4 (KTU84P) for the Nexus range of devices. If you have not heard of factory images, the quickest explanation of these is that they are a way to effectively reset your device. If you are one of the people who are constantly flashing or installing alternative or customs ROMs then you are effectively installing the opposite to a factory image. Google release these images as a means for its users to re-flash their device back to a stock state. This is rather helpful if you want to sell the device, check out the new features offered on stock or just simply undo the effects of custom ROMs.
Although Google did release the factory image for Android 4.4.4 already the original release did not include the factory image for the LTE variant of the Nexus 7. Although it has been awhile since the original release it seems Google had not forgotten about the LTE version and have today released the factory image. If you are interested in installing it then you will need some knowledge of flashing. You will need to have the fastboot tool installed on your computer which can be obtained from the Android Open Source Project (AOSP). In addition, you will need to make sure your computer has up-to-date USB drivers for your Nexus 7. Once these are in place you can use the fastboot tool to firstly make sure your bootloader is unlocked (this is necessary for flashing the factory image) and then using fastboot to execute the flash stock command. Once the factory image has been flashed your device will automatically reboot.
At this point is it recommended you then lock the bootloader again for security reasons. It is worth noting, flashing the factory image will delete all your current data and information on the device as it effectively wipes clean the device. So do make sure you backup everything you want to keep before beginning. For a more detailed description on the procedure of flashing the factory image and of course the actual image needed then head over to Google's relevant factory image page on their developer site by clicking here.