While there are the Demon's who are evil, although some act neutral. And there are Naaru, which are embodiment's of the Light.
There are some "beings" which have made appearances through Warcraft and WoW, including the GoAK that Paladins summon, Spirit Healers, and the angelic being that paladins summon in W3 to resurrect allies. There are also paintings on the roof of Wyrmrest that display 4 angels, or again angelic beings. Wyrmrest being a Titan structure built for the Aspects. Although questionable if the Titans painted the roof, or if the Dragons redecorated.
Priests can also become or channel Light to become archangel's for a short amount of time. Or in the case of Shadow Priests, Dark Archangels with the glyph. And why would a priest have angelic wings if no angels exist in Warcraft. Just food for thought.
And some references to seraphs:
http://www.wowhead.com/item=23014# and
http://www.wowhead.com/item=23014# being the two main ones, although there is what I presume to be a whole bunch of Priest Scroll of Resurrection gear listed on Wowhead.
I know, they are just ingame spells and effects, most likely associated with the Light based classes because they are likened to the thought of Angels and Heaven (Trying VERY hard not to make this into a post for religious arguement).
TL;DR -
But,
do you think there is an "Angelic" race/world in Warcraft?