Flags of the mighty Empire of Ossiden from the book I'm writing (and currently suffering a great deal of writer's block for).
If anyone is curious, the reason they use Latin is because one of the few bits of history they have clearly is that of Rome. They use terrible Latin, however (i.e. my excuse to use Google Translate for in-canon reasons).
You've got the Imperial Banner, showcasing the Imperial Crest, as well as the motto of "Deus, Imperio, Familia". It's used by most military installations and government structures.
Next is the War Flags; in Ossiden, Commoners and Nobles are separated in the military, and every unit flies one of the two banners to let their blood status be known. Most generals use reports of where noble and commoner units are to plan strategy, with commoner units flagged immediately as cannon fodder.
Finally is the flag of the University of Artificers, in which those with natural talent for advanced mathematics and science (viewed as close to magic) are gathered to study and practice their skills (against their will in many cases; people of such intellect are seen as a threat to a peaceful populace). They spend their time recovering lost knowledge, reinventing science, and crafting new theories and plans (mostly for war machines).
There's also the Chime of the Empire, which most Ossidanes sing as anything from bedtime songs to military marches. Fidelis Aeternum is the motto of the ruling house, the Teeg Family.
And we have the seven ancient laws, being the first few laws created back when the Empire was a small enclave in the Vesta Mountains.