The Amberstones give us this, more or less, about the feathers:
The reference is Qabalistic. Temperance is the direct path to the sun at the center of the Tree. The Archangel Michael spreads his wings around the corona of the sun which is seen in the rays around his head that emanate from the sun disk stuck on his forehead. The wings are an umbrella covered skinned with a selective radiation filter, offering protection from the light and the heat of the sun but still allowing the heat and light to safely penetrate and transform (to warm and tan without burning?) anyone who has made it this far.
Their section on angels is more itneresting for me since I had not been exposed to much of the information they have gathered. The brief mention of melachim in the Jewish tradition became a complex social and bureaucratic hierarchy in the Christian tradition. Seraphim, cherubim, thrones, dominions, virtues, powers, prinicpalities, archangels and angels make up the the nine choirs of beings said to surround God. The allusion to flight and the presence of bird-like wings was a construct, apparently, in an attempt to give human form to the office workers and warriors of heaven.
The wings adorning Smith's angels, as seen on Lovers, Judgement and Temperance, seem to be drawn from the same model but they appear highly stylized to me. Compare them with, say, Audubon's hyper-realistic wings.