Early Christian Art did not depict angels with wings. Often angels were not shown in human form at all but instead were illustrated as doves or even as the hand of God.
It would seem that the whole idea of showing angels with wings is simply a device in Art, especially in painting, so that the observer could distinguish between the earthly and celestial figures depicted.
It was after the Roman Emperor Constantine and the Council of Nicaea in 325 AD that angels were commonly shown as having wings in all forms of Art.
Any author embarking on writing a story or a full length novel based upon spiritual warfare must first do his research. Spiritual warfare is an extremely interesting subject and offers a rich tapestry on which to weave an exciting and dramatic plot and it presents the writer with fascinating materials in which to explore ethical, philosophical and spiritual truths.
It is a very controversial subject and in Christian circles the spectrum of opinion ranges from total skepticism and disbelief to obsessional beliefs that everything has a demonic origin.