index.xml
<Alloy>
<Window>
<ImageView id="cake"></ImageView>
</Window>
</Alloy>
index.js
var cakeArray = new Array();
cakeArray[0] = "shortcake.png";
cakeArray[1] = "montblanc.png";
cakeArray[2] = "creampuff.png";
var cakeSelect = Math.floor(Math.random() * cakeArray.length);
$.cake.image = cakeArray[cakeSelect];
$.index.open();