There was a concept art with an Argonian somewhere, I guess. It could be pretty old though...
True, so we can't say we haven't seen pictures at all, but the image doesn't allow us to see too many details, and it's only concept art, meaning that there's no guarentee they'll look the same once they make it into the game. That's not to say concept art has absolutely no bearing on the way the actual game looks, obviously it does, since concept art is what the modelers base the in-game artwork on, but things can sometimes change when they make the transition from concept art to in-game models. Whether Argonians will be the same or not I don't know.
I'm hoping that we'll see them soon myself, because this is something I really care about, Khajiit and Argonians are my two favorite races in the series, and next to orcs, they're the ones I'm most likely to play in Skyrim, so naturally, I want them to look good. Now, Morrowind's version may not have been ideal, in a large part because, let's face it, the animations were bad, but I liked how they were easily recognizable as different from the other races, not just their faces and the presence of tails, but even in the way they moved, even if this meant they couldn't wear boots and full helms, and Oblivion's change in this regard was, I felt, a step in the wrong direction. Todd seems to have indicated that they're paying more attention to making each of the races look unique, though, so if Bethesda can deliver on that province, then it will be a good thing. Some might also take the fact that they've so far refrained from showing any clear pictures showing Khajiit and Argonians, or really, any non-human races from the front as a sign that they're saving something really impressive for us. However, if it turns out instead that the results are underwhelming when we do see them, than the dissappointment will only be compounded by the fact that Bethesda made us wait so long to see them.