var randnum = Math.random();
// Change this number to the number of images you are using.
var inum = 109;
var rand1 = Math.round(randnum * (inum-1)) + 1;
randnum = Math.random();
var rand2 = Math.round(randnum * (inum-1)) + 1;

var today = new Date();
var day = today.getDate();
if (day > 15)
{
day = day-15;
}
if (day > 15)
{
day = day-1;
}