How to Make Echo Random Image

I am looking to have posts echo a random image from, say, a selection of 3 images.

I want it to echo img1 or img2 or img3.

Here is what I have thus far:

echo '<img src="http://ift.tt/1DDdhRt" />' || echo '<img src="http://ift.tt/1DDdhRt" />';

How can I make this serve up a random picture from a selection?