They are based on the Drow from Forgotten Realms (in some places in DF, even their names were Drowish). Slavery, Assassinations that go unpunished, Great Houses, Evil gods (in past... and Mephala is similar to Lolth in some ways)... they are basically the Drow.
Of course, Betehsda made good job of using the base of Drows and adding many, many unique elements so they feel and are an unique culture. They are not based on any Real Life Culture and even their real base can hardly be called that (tough I think gamesas mentioned few RL cultures like Egypt as being an inspiration).
Listen. None of the races are an exact copy of any real-world culture or ethnicity.
None of them.
Not even the Imperials are exactly Roman. There are many Roman and Greek influences but their history is much different.
This is a different world.
The way the universe is set up and has evolved in the Elder Scrolls universe is fundamentally different from our own.
The Dunmer are Dunmer. They were Velothi or Chimer. Before that they were a rebel group of Aldmer who believed in Good Daedra. Before that they were Aldmer. Before that? I'll leave such speculation to loftier minds.
Base is just a base, not a copy-paste. You have a base on which you build other elements and if you succeed, you get something unique.