Although I might be a bit too late, still I want to have all the info about M&M X easter eggs available (and I know there's a lot). If such topic already exists, please give me an URL as I couldn't find one.
Sorpigal-by-the-sea - the third "starting Sorpigal" in the series (after Sorpigal in M&M I and New Sorpigal in M&M VI).
Lord Caneghem (author of history books) - John van Caneghem, founder of New World Computing and creator of Might and Magic I to IX. History books explain the events behind all previous M&M games.
Caldwell (Sorpigal blacksmith) - Mark Caldwell, employee #1 at New World Computing.
Jassad Attqua (Sorpigal tavern) - Jatt from Might and Magic books.
Ryu (Karthal tavern) - Peter Ryu, Arcomage (M&M VI card game) creator.
John (The Deathmatch blacksmith, Karthal) - John Romero, who ported M&M II on Commodore 64.
Brenda (Cosmic Circle potions shop, Karthal) - Brenda Brathwaite-Romero, John's wife and game designer/writer of Wizardry 8 of which Cosmic Circle is important area.
Limbo (optional after-endgame dungeon) - kudos to New World Computing office dungeon in Might and Magic VI.
That's what I recognized from the first sight. Hope you've got more easter eggs for me )