Eh, that's a clever observation. Except the Fuuma!Kamui angel wings make biblical sense. The Chi no Ryuu are sometimes called "angels" while Ten no Ryuu are "seals", making a reference to the book of revelations. So if Fuuma and his dragons are "angels", he has to have angel wings.

Meanwhile, Maru and Moro have little wings (one angel/bird, one devil/bat; can't remember which one has which) in their outfits, too.