Marvel really does need to create angelic beings -- not just bird men with mystical backgounds, but angels by the classic definition. I know the Celestials are metaphorically meant to represent the heavenly messengers of the Creator, but it wouldn't hurt to drive that point all the way home with beings that actually look and conduct themselves like angels. Heck, spare no detail, including using some of the more commonly known classifications, e.g., the Seraphim, the Cherubim, Angels of the Throne, Archangels, Angels of Dominion, Angels of Principality, Angels of Power, Angels of Virtue, etc. If they're going to have all of these demons running around, it's only right to give equal time and treatment to their opposite number. After all, according to several religious traditions, most demons started off as angels.