I don't think so, i have already seen the whole series and the styles are very diferent.
Also someone told me that it comes from a 3 episodes OVA licensed around 2000.
Fanart doesn't always follow the same artistic style of the series , and the pic looks like a reasonable facsimile of Signum (if I could find a 1680x1050 or 1920x1200 version I would use it as my wallpaper again)
this is just the impression it gives me, it could be something else (in which case I have no idea what it could be)
well it's that i have seen that picture in so many forums before and the image also changes in it's backgrounds, and that makes me think that is so popular to be just a fanart, but thanks anyways.