Cultural Outline

The E1MS was an old and traditional culture, bureaucratic and hierarchical in structure, and provincial in outlook.  As the Empire developed, a rigid caste system took hold.  As star-systems were conquered, a network of stargates was built to allow direct travel, and ships with hyperdrives were used less and less, limiting exploration.  

Architecture:

The vast majority of public and official buildings were in the traditional Imperial Style, which was simple without being minimalist, with plant and leaf motifs being common.  The Imperial style typically included a moderate amount of decorative elements, including large murals depicting imperial values and historical figures.  There were also a multitude of local styles, but these were dwarfed and dominated by the official architecture of the state.

Art and Literature:

Imperial art was based on a highly traditional body of classic works.  Typical literary subjects included fables espousing a reverent attitude toward authority, the virtue of hard work, and historical literature.  "The Touch" was a famous painting depicting the transition from insect-based pollination to direct mating in Cielioids, but it was not considered pornographic, because it did not show the seasonal coloration of the lovers.

Clothing and Fashion

Cielioids generally did not wear clothing.  Certain high-ranking castes, and certain officials did, but it was usually purely ornamental in nature, designed for showing status and position.  The other conquered races generally wore clothing appropriate to their cultures of origin.

Food

The Empire was known for a wide array of cuisines and dishes.  Notable foods included:

Numguinitiso paste was a Vangalri condiment, derived from Blovonde a pudding-like dish eaten as a dessert.

Language

Imperial was the official language of the Empire, and was an educational requirement for all citizens.  The Imperial writing system was standard across the Empire, but there were several modes of pronunciation, because different intelligent species have different vocal organs.  Luckily, the diversity of vocal organs in the galaxy was underpinned by a number of similar anatomical structures, so a only relatively small number of pronunciations were necessary.  A large number of local languages were still spoken on the conquered worlds, but over time these tended to decrease in popularity.

Language Notes:

The Name Kly Fnofcob refers to a hypothetical ideal citizen.

Numbers

The numbering system used by the Empire was similar to the one we use, except that it is base-8.

Religion

Early in the Empire's history,  the upper echelons of society were constantly overtaken by religious manias.  In fact, at one point an insect-cult was in ascendance, and the old emperor even adopted an Insectoid as a son.  The old emperor died, and the insect-emperor reigned for a brief period, but was largely a powerless figurehead, propped up by religious advisers. 

The Cielioid Philosopher subspecies was engineered to help with this situation.  After one of these Philosophers started seeing mystical visions, Gronnic Polymancy became the official state religion.  Other beliefs were tolerated as well, as it was primarily the religion of the upper castes.

Gronnic Polymancy faded in time, as more imperial subjects began to identify as secular.  It did experience a revival during the 1,000 Years War, but this did not last, and after the war, the Official Schools of Philosophy were founded. 

The Official Schools of Philosophy did not teach about any supernatural beings, but did promise a happy afterlife to those who served the Empire.  Mostly, their teachings were logical and pragmatic, with a bias toward supporting the status quo.

Insignia

The Imperial Star was the Official insignia of the Empire of 1,000,000 Suns, and as such appeared on flags, state documents, state vehicles, etc.  Proud citizens often displayed the Imperial Star.  The insignia should not be confused with the military honor of the same name (although the medal worn by honorees does bear the insignia).

Variations: 

The Emperor's Star was the official insignia of the Emperor.  Misuse of this insignia was punishable by hard labor in the heat-mills of Scharlaff.