Xyth, although I understand that this is a difficult task, can you please post what states, nations, cultures etc. do you understand under each civilization? This will help in several ways:
1) Not asking about civs that are already represented in your opinion.
2) Helping with the current leader addition project.
That is indeed a difficult task. Most should be obvious from leader choice thus far but I'll list some where I think the definition may seem a bit unclear. Unless there is a relevent civ (America, Brazil), you can assume that all colonial countries are or could be covered by their 'parent' civilizations.
Scandinavia: All the northern Germanic peoples. Excludes the Finns obviously.
Hungary: Currently covers the Hun but that will probably change at some point.
Berbers: Mauretania, Numidia, the Tuareg, the Almoravids, the Almohads, Morocco, Algeria, Tunisia, and many bits in between.
Mali: All the Mande kingdoms and empires, namely Ghana, Mali and Songhai.
Kongo: The kingdom itself but also it's ethnically and culturally related neighbours, most of which were vassals or allies at some point.
Sumer: Sumer and Akkad.
Amurru: The Amorite city states of Mesopotamia and Syria, notably Ebla, Halab (Aleppo), Mari, Babylon and its empire.
Hatti: The Hittite kingdom, some of its vassals and related allies, and the Neo-Hittite city-states of Syria.
Arabia: Also includes regions like Egypt and Iraq that became predominantly Arabian (ethnically and culturally) after the conquests.
Persia: Pretty much all Iranian peoples.
Kushan: Also includes their origins as part of the Yuezhi in the Tarim basin, as well as their empire in what is now Eastern Iran, Afghanistan, Pakistan, and other parts of Central Asia. This region has been under the control of numerous civilizations over the centuries. The Kushan don't begin cover all of its history but they were the most interesting and important choice in my opinion.
Turks: Still working out what this civ covers. Will probably narrow the definition to the Turkish people that moved westward into Mesopotamia and Anatolia. I don't consider the Seljuk and Ottoman Turks to be different civilizations; they're just different dynasties. It gets messier further back in time and further east though. I don't feel any great need to go back as far as the Gökturks or the Uyghurs. Much more research needed on the periods in between though.
India: Northern India. Despite the diversity of the region, northern India has been reasonably united politically and culturally for much of it's history. Excludes the Harrapans however.
Tamil: Southern India, where Dravidian people and culture were (and are) preeminent. I think I will rename the civilization, 'Tamil' is much narrower in definition than I thought.
Indonesia: Also covers much of Malaysia.
Polynesia: Just Polynesia, not Melanesia, Micronesia or other peoples of the Pacific.
Anasazi: The Anasazi and related cultures like the Mogollon and Hohokon, and their descendants: the Pueblo, Hopi and Zuni in particular.
Aztec: Not just the Mexica, but also their predecessors and related contemporaries. This includes the Toltecs, who weren't actually a real people, but actually a mythologizing of aspects of the region's past.
Inca: Currently just the Inca themselves, may expand the definition in the future if appropriate. Research needed.
Let me know if you have any specific queries about or beyond the above.