I've just started looking over this thread per Zap's suggestion. I'm not sure if uits been brought up yet but one civic category I've only once seen represented was "Territory". This would refer to how different parts of the country are organized with regards to leadership, importance, and responsibility. In other word, it determines what ethnic groups or territories lead lead, which peoples are served first by the government, and how each territory or ethic group contributes to the empire as a whole. These are all the options I can think of.
o Hegemony - The base setting. This simply means that one city amongst your people (your capital) has risen to prominence and leads the other cities. Other cities are likely important as well, but for one reason or another, they are satisfied to allow this city to be the seat of power, s long as their interests are not disregarded for too long.
o Confederacy - This means that several peoples with a similar cultural background have come together in a loose alliance to further each others' interests. Every major city has likely demanded equal representation and power in this alliance and only contributes to the nation's well being when its own interests are directly served. No one is oppressed or abused, but not much generally gets done either.
This is as good a place as any to present my personal definition of what an empire is. An empire consists of an imperial domain and several outlying territories. The "imperial domain" may consist of a territory, city, or ethnic group. In an empire, the purpose of the "outlying territories" is always to serve the needs of the imperial domain.
o Tributary Empire - Here, one city, ethnic group, or territory has risen to prominence, likely through military prowess. They have gained power over a group of foreign cities, ethnic groups, or territories but have little interest in controlling them directly. Instead, they are satisfied with simply demanding tribute of their subjects. This tribute usually comes in the form of resources, money, troops, and laborers. Each territory is required to meet a certain quota and if they don't, the imperial military as well as troops from every other territory of the empire come knocking at their door. Unfortunately, tribal loyalties and the transient presence of imperial authority results in frequent uprisings, but the general purpose of such an empire is often simply to permanently weaken neighbors of the imperial domain and provide buffer states against invasion.
o Provincial Empire - Here, one city territory or ethnic group has risen to power and now governs over several outlying territories. Like in a tributary empire, the provinces are expected to work to further the interests of the imperial domain, however, imperial control over these provinces is more direct. Imperial governors are appointed over each territory and the empire has certain limited responsibilities towards its subjects. Public works projects are often carried out in the provinces and the provinces are protected by a standing imperial garrison. Limited attempts are also made at culturally integrating the outlying territories into the the imperial domain.
o Viceroyalty - Here, the imperial domain has imposed a subject feudal system on its outlying territories. This system has its own king (called a viceroy) and feudal lords as well as its own capital. This entire system however is subject to the rulers of the imperial domain (and their political system, whatever it may be). A viceroyalty usually exploits its subjects to the point of exhaustion for the extraction of local wealth and resources. This is done usually because of the distant location of the outlying territory or due to the complete absence of imperial culture. In any case, viceroyalties are lucrative but become increasingly unstable as provincial resources become exhausted.
o Colonial Empire - Here, the imperial domain has settled or conquered cities on foreign soil in the presence of strong foreign culture. The territory is set up as a colony and made economically dependent on the mother country for traded resources. The colony's populace and territory are exploited to create a stable market for the mother country's products and to allow a military presence in the colony's location. Colonies, however, are jealously protected by the empire and are generally allowed home rule to an extent, the form of which they are allowed to choose. They are, however expected to conform to the values and lifestyle of the imperial domain, spreading the culture and religion of the mother country.
o Nation-State - In a nation-state, self-determination is the pervading line of thought. One ethnic group rules, but only where that group is dominant. Each nation-state includes only as many people as are necessary for economic success and military protection. The peoples of a nation-state must share a similar cultural background, therefore, its territories tend to be geographically linked and its boarders tend to conform to natural boundaries. Nation-states have little or no interest in acquiring new territory, but are very interested in exporting their culture and values to other states. They also fiercely defend their territorial boundaries and all peoples of a nation-state feel necessarily obligated to defend their country.
o Federation - In a federation, several cities, territories and/or ethnic groups have willingly combined to further their collective interests. Unlike in a confederacy, members of a federation assume that what is good for one or a few of the members is good for the whole, therefore all member are obligated to protect the federation's interests regardless of whether or not they are directly benefited. Several states and territories with diverse backgrounds may be included and all will likely demand to be represented equally, but they have no right to oppose the decisions of the federation's executive body. Cessation and non-cooperation are met with military action.
This civic would likely have a strong effect on your civ's name and affect maintenance, rebelliousness, culture, and happiness heavily. Viceroyalty should also make viceroyal palaces possible.