I think wings are a great way to symbolize a "higher being".
In Shade's case, they used as visual proof of his mastery of all Elements later in the series,
and also how much of Shadusk's power he's tapping into before he achieves Master of Elements.
When Shade shatters the chains around his arms and legs, one pair of wings grow.
Breaking the chain that runs down his coat splits the wings into another pair.
Destroying the chain belt makes the final pair.
