function image() {
};

image = new image();
number = 0;

// imageArray
image[number++] = "<img src='http://www.brits-on-the-pull.co.uk/ecards/ecard_images/thumbnails/tn_flasher_2.gif' border='0'>"
image[number++] = "<img src='http://www.brits-on-the-pull.co.uk/ecards/ecard_images/thumbnails/tn_want_pussy.jpg' border='0'>"
image[number++] = "<img src='http://www.brits-on-the-pull.co.uk/ecards/ecard_images/thumbnails/tn_highlander.jpg' border='0'>"
image[number++] = "<img src='http://www.brits-on-the-pull.co.uk/ecards/ecard_images/thumbnails/tn_nice_flaps.jpg' border='0'>"
image[number++] = "<img src='http://www.brits-on-the-pull.co.uk/ecards/ecard_images/thumbnails/tn_self_blow.jpg' border='0'>"
// keep adding items here...

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

document.write(image[increment]);