The artist might have been thinking about the Norwegian forest cat, a longhaired breed that this creature resembles. Aside from the huge wang, that is.
I'm under the impression that Giants in oblivion take a background role as an extinct society. I might be wrong, the last time I played it it was three or four weeks after it came out. Its probable that I encountered them without knowing what their name was, but I don't remember the Valvalo either, though the name is strikingly similar to 'Valvalis', another famous RPG character.
