Used:
Forgotten Empires
Rise of the Rajas
African Kingdoms
Dawn of the Dukes
Last Khans
Lords of the West
Mountain Royals
Dynasties of India
added by @Skadidesu
Left:
Prince
Governor
Monarch
Noble
Jarl
Tsar
Keiser
Basileus
Getman
Caliph
Sultan
Emir
Sheikh
Malik
Pasha
Bey
Shah
Noyan
Chief
Leader
Ruler
added by @Hzdrafxx
added by @Mahazona
Well , left ones are more than used ones. 
I think the devs need to get more creative. They can reference the region of the world that the expansion centers around. For example, my Caucasus and Oceania expansion concepts are called Pride of the Caucasus and Powers of the Pacific, respectively. In both cases, no special titles are referenced, but the places that the expansions center around. If the devs run out of ideas, they can do stuff like that.
Best naming concept so far sultans ascend adds byzantines and japanese 
Voivode is also a term that can be used for a dlc name.
Like⊠you could always be more creative.
Secrets of South America. Treasures of Mexico. Path to the Orient. Land of the the Horse Eating Flies.
A little whit can go a long way and not need something royal in it.
AoE3 used âKnights of the Mediterraneanâ, or just went straightforward for like âUnited States Civilizationâ if the expansion has only one civ
This could be reused in a DLC focusing on the Chinese region - Dynasties of China.
I would pick something a bit more original than just âdynasties of Chinaâ. Maybe something like âSons of heavenâ or something related to the Mandate.
Powers is possible as it means entity.
For Pacific , I also suggest Captains.
âRulers of the Sahelâ - Soninke + Hausa
We need more African civs 
.
Rivalry of Yellow River or just Rivalry of Rivers. Introduce northern China civs like Tangutese, Jurchenese, etc who invaded Chinese (Han) multiple times throughout history, and usually the Yellow River as the borderline between these powers. And the Yellow River is also very important for Chinese culture
Yes, that name can also work. I suggested something related to the Mandate because I find it quite unique to China.
But any name that is not a carbon copy of the name of a previous DLC is fine by me.
Please forgive my ignorance.
Whatâs this? 
Southern side of africa.
tsetse flies attack horses so those areas did not have horses.
Doge (of venice) is another term.
Bishops marquise Popes are also possible combos.
You inspired me
Knights of Crusade 
civs: Templars Malta Teuton Tripoli Jerusalem Antioch & so onâŠ
or Orders of Crusade
and
Arabian Knights
civs:Misr Maghreb Nejd Sham Yaman âŠ
Thanks
You forgot two very important ones:
Doge is reserved exclusively for Venetians, and it is important to remember that the name of the DLC should best refer to all civs included in the DLC. The Venetians civ would fit into a Mediterranean themed DLC where they would appear alongside the Aragonese and possibly the Moors as well.
X + of (or of the) Mediterranean
I think that Venetians and Aragonese civs could be added to such a DLC alongside the Jerusalemites civ (Templar Knight and Hospitaller Knight as Unique Units).
The title of doge was used for the elected chief of state in several Italian âcrowned republicsâ. The two best known such republics were Venice (where in Venetian he was called doxe [ËdÉze]) and Genoa (where he was called a dĂ»xe ############################################################################################################################# which rivalled each other, and the other regional great powers, by building their historical city-states into maritime, commercial, and territorial empires. Other Italian republics to have doges were Amalfi and the small town of Senarica
Seriously why is half the text taken out by the sensor.
Theoretically a dlc called doges of the mediterranean can have italians renamed genoese add venitians and milanese.milanese will get the current campaign.
I think itâs better to make the Italians civ more âItalianâ than to turn them into Genoa. The Italians civ icon could be changed to a compilation of 4 coats of arms (Florence, Milan, Savoy and Pisa) with the current Italians icon (itâs Genoa coats of arm) on the middle.