At present, no. Stay a while, and listen..
There is very little back story given to the inhabitants of Tristram, apart from the few that make it into the third game (one way or another). References to them appear to use the format provided by Valorum; [first name] the [occupation/title]:
- Griswold the Blacksmith
- Pepin the Healer
- Ogdin the Tavern keeper
- Gillian the Barmaid
- Farnham the Drunk
- Adria the Witch
- Archbishop Lazarus
Even the royal family only appears to be referenced by their title(s):
- King Leoric of Khanduras / The Mad King / The Skeleton King
- Queen Asylla of Khanduras
- Prince Aidan of Khanduras / The Dark Wanderer / The Warrior (as he appears, in the first game)
- Prince Albrecht of Khanduras
There is, however, additional lore that sheds light on Deckard Cain's full name. In the novel The Order, we are given the names of some of Deckard Cain's relatives:
- Deckard Cain; the man, himself.
- Jered Cain; an ancestor.
- Amelia Cain; Deckard's wife.
- Jered Cain; Deckard's son, named after the ancestor.
- Aderes Cain; Deckard's wife.
The naming pattern implies that Cain is, in fact, a surname. Furthermore, I cannot find a source, but the Diablo Wikia has this to say about Aderes, concerning her choice in naming Deckard:
Aderes lived in Tristram. She married a tanner and had a son with him named Deckard. Despite Deckard's wishes to the contrary, she insisted that he take the name of Cain, rather than his father's surname.
Biography of Aderes Cain, Diablo Wikia
While this is currently unsourced, if accurate it suggests that others in Tristram did have a surname, for Aderes to have to wish against Deckhard taking his father's. This also suggests the children took the surnames of their fathers, traditionally.
In reality, Deckard was really the only character central to the plot, throughout much of the Diablo story. It makes sense for the developers to put more effort into fleshing out his background, which may explain why he was he only one to be given a surname.