That depiction is very interesting. That could be how they look.

"I stand by my descriptions that the Akavir Potentates were serpentine, not only in temperament, but in physical appearance. Even if I did not have witnesses, there are too many descriptions of them as snakes to assume that all writers used the same metaphor."http://www.imperial-library.info/interviews/writers.shtml

I'd go with him; http://www.tamriel-rebuilt.org/forum/files/akaviri_162.png

Moreover, the idea that Tsaesci would be humanoid is the best Elder Scrolls related example of BATW.

Bipedal, you mean.

I did mean humanoid. There have been a lot of people around claiming that the human skeletons in Pale Pass were Tsaesci, which is still something different imo from snakelike creatures walking on their two rear limbs.

http://trilliumcg.com/mattsworld/Images/trogdor.jpg

I think the staff from bethesda was just too lazy to make new models

Or the Akaviri had human servants/slaves/soldiers... and as has been said, they weren't necessarily Tsaesci...

Or no one knows for sure and this question is entirely open-ended.

Or no one knows for sure and this question is entirely open-ended.

While the skeletons and ghosts of Pale Pass are referred to as Akaviri, they are never called Tsaesci. Someone postulated that the story of the Tsaesci eating the men of Akavir was a metaphor, and they were in actuality culturally absorbed.

I find the human-servants theory much more palatable though. The Tsaesci may have endeavored to take their own dead only.

EDIT: In retrospect, this is really more a response to posts on the first page than this one. If you don't want to hear a lengthy (and likely incorrect) rant about the Snake-Men of Akavir, please ignore this an continue to talk about the Selectives. Hehehehe.
For the "Tsaesci-absorb-enemy-cultures" people:

Let's get this straight. The Tsaesci are http://www.imperial-library.info/obscure_text/tsaesci.shtml Tamriel is a world of myth. You could -- could! -- say that the way that the Tsaesci "eat" people, such as the humans on Akavir, is by absorbing their culture. But look at this creation myth -- quite literally, "we ate it to become it." It's much, much more complicated.

Read the myth. Half of it is semi-technological mumbo-jumbo, but the basic idea, from what I gather, is that the Tsaesci are (or were) somehow able to take the very base identity of a god, a culture, a person, etc, its "name", and then consume it, absorbing it into their collective race's identity. This sounds very much like what you would hear about in a Dragon Break, particularly what the Tribunal did on Red Mountain -- rewriting history so that you, and in this case something else as well, are fundamentally changed, but it being as if it had always been so. In this case, the revision of history is that the Tsaesci took advantage of the shifting sands of Time during the Creation (and Merethic Era?) and rewrote their history so that the identities of previously existent (and presumably now nonexistent) cultures and even gods merged with their own, eventually creating "Tsaescance", or their ultimate form, as IMMORTAL. VAMPIRE. SNAKEMEN.

So this is what happened to the poor, poor men of Akavir. It wasn't just a matter of "cultural assimilation" -- they were consumed. Entirely. They were eaten, mythically, their very identities stolen, broken down, and melted to form the golden scales of some very greedy Snake-Men. It's more than death, and more than cultural assimilation -- it's a fate far worse than both. It's like historical revisionism, except you're the bit of history being erased (or, in this case, "reformatted.")

I can almost see these guys at a dinner party:

"WE ARE TSAESCI. WE ARE PERFECTION; PREPARE YOURSELVES FOR TOTALITY. WE WILL BREAK YOU DOWN INTO YOUR BASE MEMES...THEN EAT YOU. EXPECT US."