Names are not case sensetive but do need to be spelled correctly.
Rename an elytra to everything inside of the "quotation marks", do not include 
the quotation marks.

Elytras Names:
  "Bat Wings"
  "Blue Fairy Wings"
  "Black Wings"
  "Skeletal Wings"
  "Cape Wings"
  "Cherub Wings"
  "Fire Wings"
  "Green Fairy Wings"
  "Leaf Wings"
  "Phoenix Wings"
  "Purple Fairy Wings"
  "Star Wings"
  "Yellow Fairy Wings"
  "???? Wings"