How to display a random image on another website

There are times when people want to rotate a picture on a social networking site like Face book, MySpace, or just as a blog signature, but the restrictions are such that when you are allowed to specify an image, you have to enter a URL to an image and the content-type must be set to “image/gif.” So, how do we get around these limitations and still allow a random image to be shown? Read on.