I think ANY name can have a nickname. People will always find a way to shorten a name if they want to.
Luka could be
Luke or Luki. I think it's easier to shorten
Luka than
Ivan, personally, even thought
Ivan could be
Ivy.
I know an
Esther who gets called Esthie and a
Hope who gets called Hopie.
Eva could be
Eve,
Evie etc
I'll try, though:
Astraea (I guess she could be Aea but I doubt it would happen)
IvyKaia
Cornelius (yeah I guess he could be Corny, but I doubt anyone would do that)
NoelFinn
Still I guess creative people can shorten ANY name. It's annoying because I hardly like any nicknames either but it can happen.
Sasha could be Sash,
Poppy could be Pop or Pops or something (eek hehe). I really can't find a way too shorten
Ian, though, good one :) But I guess he could end up being called Big I or whatever, there's always a way.