I know some of these were used in Diablo 2s battle.net-screen. There was a window at the bottom showing everyone who was in the same chatroom at the time by displaying the Diablo 2 character they were logged in on, showing off its gear and brag-worthy titles (like "Patriarch").

BUT, those same chat rooms could be accessed via other Blizzard games too, they all used Battle.net after all. If someone playing Starcraft hopped into a D2 chatroom, they would appear as a marine. Warcraft 2-players would appear as an orc. The big silver paladin looking hammer guy is for whoever was moderating that chat room (guilds could have their own rooms).

There's a list on the old school Arreat Summit D2-webpage here https://classic.battle.net/diablo2exp/basics/bnetchat.shtml

That guy you think is blackthorne, to me he looks like a d2 developer. If you look really closely hes wearing a diablo 2 t-shirt. He seems to be wielding a sword and possibly a keyboard? I was thinking the other sprites (the woman with the long skirt, the guy with a blue cloak and big shoulders, and the red robes) could have been npcs that were dropped from the game at some point.

Shame none of the Lost Vikings got a cameo.

Wanna say who you think is Serious Sam is actually supposed to be that guy from Blackthorne.

Warrior D1(Aidan - dark wanderer)
Rouge D1(Moreina - blood raven)
Vizjerei sorcerer D1(Jazreth - summoner)
Starcraft 1 terran marine
Warcraft orc
Serious Sam?
Paladin? with hammer from W3?
Fire mage? from Gothic?
who are the others?