var imgStack = {};
var imgCursor = 0;

// bind functionality to clicking next
$("a.next").bind('click', function(event){

    // change the image to whats in the stack at the current cursor position
    $(".the-image").attr('src', imgStack[imgCursor]);

    // increment the cursor value
    imgCursor = imgCursor + 1;

    // get the next image value, so the cursor has something to do if they click next again
    $.get('/location/to/get/next/image/data', function(data){
        imgStack.push(data);
    });
});
// bind functionality to clicking prev
$("a.prev").bind('click', function(event){

    // change the image to whats in the stack at the current cursor position
    $(".the-image").attr('src', imgStack[imgCursor]);

    // increment the cursor value
    imgCursor = imgCursor - 1;

    // get the next image value, so the cursor has something to do if they click next again
    $.get('/location/to/get/prev/image/data', function(data){
        imgStack.push(data);
    });
});