I have created a first draft of a flag I will try and work on as time permits. This is the company standard for the Fighting 812th of Maladin Prime.
Background notes *fluff*
Not long after the Horus Heresy a company of Imperial Fists used the planet as a staging area. The Imperial Fists conscripted the citizens into military service. Using them to heavily fortify the planet in case the Traitor Chapters backtracked. They also setup a ruling party which was required to submit complete fealty to the Emperor and Terra. Because of this the citizens are strictly devoted to the Emperor. Every citizen is required to volunteer at least 5 years in military services.
After much of the galaxy was reclaimed the Imperial Fist left the planet. Over the Millennium since then the Maladin Government has insured the Emperors will is strictly enforced. During the IF occupation the military flag was changed to the current version. The latin in the flag relates to the devotion of the Emperor.
There are islands that are under strict military control. The few rumors that are whispered say there are special training centers located on them, and the troops are not dressed in the standard issue forest camo.