Basic and general statistics; at least, as much as I can get from the books. There's not a lot in the way of general information...
Planet: Asu (the Second World)
Weapon: The Lunar Mercury; also called the Lunato Mercury
Hair: Red; I picture it being a sort of darkish red, but then again that's not specified. It's normally tied back; however, that's not always the case.
Eyes: Unknown. They're a light color, though.
Outfit: A black robe-type thing with a cloak and some sort of armor over it.
Age: This is unknown, as he lives forever; but somewhere over three hundred years.
Personality: Seeu almost doesn't seem to have one; however, he's just a very quiet and withdrawn person. He sometimes evidences just a little bit of something beyond his emotionless facade, but for the most part he's the silent type.
The information in the manga is pretty sparse for all of the characters, unfortunately. The above information is the stuff that is confirmed; for more speculation you can head over to the other sections.