Google seems to always have some trouble with releasing factory images for devices. Quite a few images have been delayed for weeks or even months, while others get them immediately. Luckily, most people will have no need for them, but those who do were out of luck.
This was the situation with the Nexus 7 2013 LTE, or the “mobile” version as Google calls it. Though all the Nexus 7 factory images for the Android 4.4.4 build were released in June, the LTE model had to wait until just today to get its 4.4.4 factory image. This image will flash your entire device to stock if you ever need it.
If you want to download the image for yourself, just in case something goes wrong in your modding adventures, hit the source link and stay safe.