Yesterday I've found Flickr profile of Reciprocity - Alan Jaras - a research scientist and microscopist playing with photography of caustics and other light effects. Of course it's all the matter of taste, but for me his photos are really amazing. They look so abstract and so natural at the same time. Just look at the galleries Taming Light, Bending Light and Twisting Light. I think it wouldn't be easy to procedurally generate such images. Also check out his Favourites for more unusual images.