I'd definitely say the image in question is a Dwemer ruin. Admitably, it's not identical to Morrowind's Dwemer ruins, but I didn't expect it to be, and with all those pipes and that steam, I can't see what else it could be. It has also generally been assumed that the Markarth screenshot is one of the cities built into Dwemer ruins we've heard about, and the style of that picture definitely looks like it could be what those structures might look like on the inside, so I can believe that. Also, we can expect to see centurion spheres in Skyrim, as one of them shows up in the Sounds of Skyrim video where the person in it is demonstrating a sound that is being used for them.
In any case, it definitely looks like dungeons will be more interesting than Oblivion this time around, really, all environments promise to be better from what I've seen.
Does anyone have a picture of a Dwemer? Apparently there have been two in game?
There has been one living Dwemer in the Elder Scrolls series so far and as far as we know, he is the last one left, and he was http://images.uesp.net//d/d2/MW-creature-Yagrum_Bagarn.jpg Aside from that, in Tribunal, the player encounters one Dwemer ghost who can speak to the player, he looks http://images.uesp.net//c/c0/TR_Creature_RadacStungnthumz.jpg.