While playing through the "Chasing Echoes" chapter of Dawnguard, you'll come across a female Feral Vampire inside Castle Volkihar. She wears bloodied versions of ragged trousers and footwraps as seen http://www.uesp.net/wiki/Skyrim:Feral_Vampire. Of course, on female characters 'ragged trousers' do not appear as trousers because this would leave a female character topless (and by God, we wouldn't want that to happen), so they appear identical to a roughspun tunic whenworn by females. Now, if you're playing a female character and you put on the bloodied versions of the ragged trousers and footwraps, they'll appear just as they do in the linked picture of the Feral vampire.
But if you're playing a male character, they'll appear on you as light lavender pajama bottoms with matching slippers. Pretty funky. I wear them around the house.