function image() {
};

image = new image();
number = 0;

image[number++] = "<img src='http://www.egiptologia.com/sce/images/randominterior01.jpg' width='758' height='40' border='0'>"
image[number++] = "<img src='http://www.egiptologia.com/sce/images/randominterior02.jpg' width='758' height='40' border='0'>"
image[number++] = "<img src='http://www.egiptologia.com/sce/images/randominterior03.jpg' width='758' height='40' border='0'>"
image[number++] = "<img src='http://www.egiptologia.com/sce/images/randominterior04.jpg' width='758' height='40' border='0'>"

increment = Math.floor(Math.random() * number);

document.write(image[increment]);