@ Elothan: I think if it's recognizable as a cloud it qualifies, but if you start using man-made "clouds" like mushroom clouds or smoke stacks or jet contrails, you risk losing votes because you're on the edge. Sometimes that pays off because folks like out-of-the-box thinking, sometimes they feel you didn't honor the challenge. It's a gamble. In the end, the voters decide who followed the rules.