They have, both to look like a weaker ship like a merchant vessel (Q-ship), or to make a military dummy look like the real thing. Although I can't say I've heard of an armed ship pretending to be a bigger armed ship, seems like that would be counterproductive, since it would tend to draw more fire than it can handle.Just an aside. I wonder why no one ever thought to have camoflage look like a superior mirage of a different kind of vessel...I've seen dazzle camo...