This question was prompted by my search for an image to illustrate the words of John Milton which I posted a few days ago. I found all kinds of images, but not one that I would fell comfortable using.
The question may seem frivolous, as the Bible does not give a clear description of an angel. There are descriptions of seraphim, cheubim, living creatures in Ezekiel, and living beasts before the throne of God in Revelation. I don’t know if anyone has really succeeded in drawing a picture that accurately represents those descriptions. These beings have some role in God’s kingdom, but just what it is isn’t exactly clear, except that they are continually praising God.
Angels are something a little different. The name means messenger and is used in Revelation to describe the human messenger, or minister, of each of the seven churches of Asia. The celestial angels appear to have the specific responsibility of being God’s messengers to mankind and also protectors of mankind.
In the few mentions we have of an angel appearing to individuals in the Bible, he is usually described as appearing to be a man. That is, the angel appeared to be human. That would preclude wings. Though the other beings are usually described as having wings and flying, angels appear to simply step from the unseen celestial realm into the terrestrial.
Angels appear to have no gender, “neither marry, nor are given in marriage,” thus depictions of angels in sensuous feminine form are clearly false. For the same reason, it is probably correct that angels are never depicted with a beard.
Thus, the best I can do to describe an angel is to describe what is probably not part of his appearance: no wings, not distinctly masculine or feminine. Sometimes an angelic appearance is glorious, often there is nothing startling about the appearance of the angel.
The ministry and purpose of angels is more important than their appearance, for that reason I will quote Hebrews 1:14 as the conclusion:
Are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation?