i.e.
for a game set in Skyrim = i) Orsinium. ii) Roscrea (island captured by Uriel Septim V that was Annexed by Solitude in the late Third era)
for a game set in Black Marsh = i) mainland Morrowind. ii) Esroniet, Yneslea & Cathnoquey (islands between Akavir & Tamriel that were capture by Uriel Septim V)
for a game set in High Rock = i) Atmora (& Aldmeri if both are the same place as names are curiously similar) - if it doesn't feature as a dlc for Skyrim that is.
for a game set in Hammerfell = i) Thras (would offer a good contrast to the sandy deserts of Hammerfell) . ii) Yokuda (hopefully a land of the undead - the land died)