Well, Dashenka and I are planning to make romance triangle between DK male belf, paladin female draenei and warlock female belf. Dashenka likes play either draenei or belf but this is basic idea;
Male belf DK; He was blood elf male paladin, who fought in The Burning Crusade. After events in Sunwell he joined Argent Dawn during scourge invasions where he befriended female draenei, fellow paladin. He got serious crush on her (perhaps start of relationship) but he died while saving her. He was then ressurected as Death Knight.
Female draenei paladin; Pretty much same story as above. But naturally she may feel disgusted or disturbed (up to writer of this char) that her former lover is now a death knight but has (or maybe) grown (secretly) fondness to male belf DK's childhood friend.
Female belf warlock/x class (can be any really but warlock for kicks and nice trio dynamic); Female belf is childhood friend of male belf DK, had always got crush on him but had never been able express it directly. Only clearer signs of her interest is that she have got jealous behavior when male belf met with female draenei secretly (while alive) and still got jealous emotions when whole romance triangle restarts again.
Idea is that story starts during ghoul invasion, male belf dies, then short scene in Ogrimmar when platoon of death knights arrive inform birth of Ebon Blade and then belf and draenei female learning that male belf was now a DK. It would continue from that into missions done for Argent Crusade/Ebon Blade and both factions in war effort against lich king.