Barring things like sharing Suramar (night elves) , sharing Silvermoon (void/high elves), sharing darkshore or Theramore (forsaken)
Night Elves:
For me, I think if they designed a night elf city like Zin'Azshari in warbringers use to look like, that would be very cool.
As for High elves:
Take a look at this: It's Skywall, I don't know about you, but it just screams high elf. If return to Silvermoon never becomes an option i'd go for that.
Forsaken:
I think Icecrown Citadel would be very fitting and grand. Alternatively they could do something with the ruins of Theramore.