Coming up with Yuan-ti names...

[Mallus]

Honestly, I'd forgo the cornucopia of "s" sounds and the apostrophes that are bound to go with them and borrow from Chinese/HK martial arts film nomenclature, i.e. Smiling Snake, Jade-Faced Snake, Boss Snake, Sober Snake, Solid... err.. wait, no... Laughing Serpent, etc.

edit: now I want to play a Yuan-Ti Drunken Master monk named "Sober Snake". He'd be something of a liar.

 

[CapnZapp]

Heneis the Mind Whisperer of Sseth
Undead of Zehir led by Uhlaash the Mummy Lord (thx Turanil!)
Sitlali the Priestess of Dendar the Night Serpent
Talatiall the Pit Master of Mershaulk

Names from my (expanded) Ruins of Hisari preparations

 

[Gradine]

Yuan-Ti are actually modeled over the Aztecs. Though I see them using similar but with more "s" sounds

Fantasynamegenerators has a Coatl name generator that might be appropriate in this instance:
www.fantasynamegenerators.com/quetzalcoatl-names.php

Again, might just want to sub in some "s" sounds where appropriate.

 

[Sunseeker]

Personally, if you have to hiss a bit while saying the name, it's a good fit. So th sounds, lots of "S" and "I" and maybe an apostrophe or two. I always figure Yuan-Ti to be sort of the snake-people version of Drow, rather long names with some combination of house and order and such.