How do I change the factory settings that an Android device reverts to? 'm looking to change some of the default settings that a device reverts to such as language, timezone, resolution.

Is there a way to do this through the terminal assuming my device is rooted?
A factory reset simply wipes the userdata partition (and sometimes some extra cache partitions as well, but that doesn't matter). This resets all settings to the defaults set in the system image.

Exactly where in the system image is different for different settings. For example, some things come from the build.prop, which is relatively easy to change with root: you just mount the system partition read-write and edit the file. Most settings that you'd change through the Settings app are stored in that app itself, so to change those defaults you'd need to edit the APK of that app or install a custom ROM.