That's no Seer, that's a Striking Scorpion. The helmet tassel, mandiblasters and repetition of the Striking Scorpion rune gives it away. It is still very different art though.
Now that you mention it, it seems rather obvious. I was just thrown off by the colouring of the armour and the cloak.
Welcome back, Farseer. Haven't been keeping up with the forums lately, myself, but as a pointer to a discussion we were having some time ago about non-human looking Eldar, here's a randomly found sketch that looks very interesting Here's the dude's DA account: http://rayph.deviantart.com. He really has an intriguing way of drawing 40K.
Not sure if this has been posted yet, but if it has, it must be posted again! This guy has some awesome fluff and badass weapons.