This answer has a number of example images and a link to the website that produced them. Following the link allows viewing the code that produced them, but the only explanation given within the answer is:
I've found that bump mapping can add a lot to the look of ice. Using bump maps both when calculating refraction rays, and when calculating lighting
To me this sounds intriguing and makes me wish there was more detail, rather than just external code and pictures. I feel that the explanation would make this into a complete answer.
While this is my personal preference, and affects my voting, what should our policy be? The policy will determine whether answers are flagged or simply not voted as positively.