Dragonmen, they're fusions of humans and dragonspawn that were created by Nefarian. I think one of them also makes an appearance at Blackrock Spire as a part of the Iron Horde as well.
They share the same skeleton/animations as worgen.
My own fanon concept would be 'Black Dragonsworn'. My idea was that assuming Ebonhorn joined the Horde alongside the rest of the Highmountain (which he does), Wrathion would become his counterpart. Basically Wrathion using some sort of Titanic technology to create a new batch of dragonmen able to shift from human to draconic form through training.
The humans themselves having unique skin and hair customization options with an Arabian aesthetic modeled after Wrathion's human form.
Bad fanfiction? Probably.