From my take a "vampire thrall" would be more along the lines of a familiar/human subordinate-
the original mentioning of this can be found in the Pax demo impression thread here: http://www.gamesas.com/index.php?/topic/1225436-my-pax-demo/
not too many people made mention of this little piece of information,I would like to get across what exactly a "thrall" is by definition and to see what everybody thinks about this subject-

definition for thrall :

[ Thrall (Old Norse tr?ll) was the term for a serf or unfree servant in Scandinavian culture during the Viking Age. Thralls were the lowest in the social order and usually provided unskilled labor during the Viking era.[ Thrall is from the Old Norse tr?ll meaning a person who is in bondage or serfdom. The Old Norse term was loaned into late Old English, as tr?l. The corresponding native term in Anglo-Saxon society was teow or esne.

The term is from a Common Germanic root *treh- "to run" and the Old Norse term in origin referred to "a runner". Old High German had a cognate, dregil "servant, runner".]

http://en.wikipedia.org/wiki/Thrall

As you can see by this definition it fits perfectly with skyrim's Nordic setting.

Sorry,I did not see anyone truly explain or touch upon this,I hope this may help clarify a few things.
From that definition I am taking it as vampire "servants"
A fresh turned lowly vamp. could be a possibility.
My money is that a vampire thrall will be a human servant/slave that probably runs errands,used for food/blood source and protects their dwellings.

What is everyone's take on this?
do you think a vampire thrall is a human servant or a lowly new turned vampire?
Look forward to everyone's opinions.

Low level vampire

Don't know...but I'd like a human servant that I can feed off of, send off to get stuff, ect...

Low level...human!

Cattle. Morrowind had cattle, food for vampires to feed on slowly. The Whet-Feng had prisoners kept catatonic so they could periodically harvest blood from them. The vile lair had a prisoner kept forever in a deep sleep. The Cyrodilic mentions the Whet-Feng were enlightened and probably copied their methods as well.

All in all, we need cattle. Vampires are in Skyrim and they are playable, so I hope the house decoration is like fallout. I wouldn't mind feeding off my own cattle now and then rather than going out to feed or waiting for a spouse to sleep.