Feh. All the archdevils and demon princes have avatars as well.
As for my alias, it is unfortunately linked to Sammael of Wheel fo Time, one of the Chosen of the Dark One (i.e. bad guys) and a great general of times long gone. To separate myself more fully from that character, I often use the title "Duke of Baator" or change the alias itself to "Duke Sammael."
Historically, Sam(m)ael is one of the names medieval Hebrew scripts attribute to Satan, although there is much debate whether or not they are the same entity. Sammael is the only fallen angel that is both hated and loved at the same time, beautiful to behold but terrible in his wrath. He is the angel of retribution and war, but also of truth and knowledge. There are several apocryphal texts that mention Sammael, although they are not parts of the "official" Bible.
The avatar is from a picture of a pit fiend (the highest-ranking non-noble baatezu) standing victorious on a pile of dead adventurers, by Wayne Reynolds, one of the principal D&D 3(.5)E artists.