I like the nightborne culture. The glowing tattoos. When blizzard announced them they said they would add more customization to them. It will be around 5-7 years before they get any though now.
I do like their silhouette. The fact that you can play a nightborne warlock is good since it’s the first night elf model to use it. Generally the males have ugly and old looking faces, the could use a more slender model. Males are lacking in facial jewelry as depicted in some nightborne male npcs. More slender models, and maybe some quad/glute muscle/ fore arm increases to get a more atheletic look.
Males could do better with some smaller noses. And lower face modificatoins such as more slender cheeks, more pronounced fuller lips, and facial metal plate jewelry (mostly around the jaws) that compliments stuff like jawline.
The females are overall in a better place. More accurate bodytype depictions, more young looking face options, nice hairstyles.
Both genders could use more slender eyeshape models.
Overall they could use more then 3 skin tone options. A greater color variance for hair color, more general hair styles. The glowing tattoos are great, I wish more was given. More eye colors would greatly be appreciated. From Highborne eyes, to Nightborne eyes. Felborne inspirited fel variants. Arcane glows. Dark elune glow blues. Silver white moonlight eyes for the night. Maybe an ardenweald/bastion blue. Some light purples/ pinks. Maybe a horde red type of magic eyes when they experience bloodlust O.o
As for unique additions, we could have arcane affected hair styles such as arcane glow, rainbow azerite glow, fel glow/ highlights, blue dragon flight fire blue, arcane white glows. Arcane colored hair as in changing hair colors from arcane variants, to rainbows, to nightish purples and blues.
Arcane tips on fingers and feet, or silhouette border shadings.
As far as transmog armor they could add more nightborne sets, floating leg/foot rings, floating arm bracelets.
In addition to this I would say we get night elf neutral customization like void elves. The moonguard elves could have joined the Nightborne and thus we get nuetral night elf customizations through them and rp as moonguard elves on horde. Another sort of bodytype they could add is undead night elves. The ones that joined the horde under slyvanas.