var imagetracker="m";
function change(){
var image=document.getElementById('image1');
if(imagetracker=="m"){
    image.src="images/momo 2.jpg";
    imagetracker="t";
}else if(imagetracker=='t'){
    image.src="images/taco.jpg";
    imagetracker="m";
}
}
var timer = setInterval('change()',2000);

var imagetracker="p2";
function change2(){
var image=document.getElementById('image2');
if(imagetracker=="p2"){
    image.src="images/pizza 2.jpg";
    imagetracker="b";
}else if(imagetracker=='b'){
    image.src="images/burrito 2.jpg";
    imagetracker="p2";
}
}
var timer2 = setInterval('change2()',2000);

<img src="images/momo 2.jpg" height="150" width="220" id="image1">
<img src="images/pizza 2.jpg" height="150" width="220" id="image2"><p>