This has nothing to do with Starcraft the game and everything to do with Starcraft the universe.
Both the game and the universe. The game is a robust real-time strategy classic, the universe one of the more enjoyable in video games, managing a science fiction setting with a dash of humour. But that universe is - like most fictional worlds - not entirely of its own making. Just like Star Wars is The Hidden Fortress with lasers, Starcraft owes a visual debt to Games Workshop's Warhammer 40K.