1) You should create spell with permanents duration, death persistent attr.
2) You should put your wing model in any game patch (in would be easier if you put it in spells directory).
3) You should create new line in spellvisualeffectname.dbc with your model and scale.
4) You should create new line in spellvisualkit.dbc. There you should write your model id (from spellvisualeffectname.dbc) in column 4. (from 0)
5) You should create new line in spellvisual.dbc. There you should write your spellvisualkit id (from spellvisualkit.dbc) in column 4. (from 0)
6) Open spell.dbc, find your spell and in spellvisualid_1 you should write your id from spellvisual (from spellvisual.dbc)
Now your model should work. If you need to attack wings on another attachment point, you should play with spellvisualmodelattach.dbc