loading dynamic images using jquery slider options?

At the moment I am having big problems with flexslider populating the slider with this script. It basically is to inconsistent in loading time and doesnt always load every url image from the script.

$(document).ready(function () {
    var urls = [
        'http://fantasyfootballpundits.com/football/?category=Captaincy+Analysis&format=json&callback=?',
        'http://fantasyfootballpundits.com/football/?category=The+Gameweek+Preview&format=json&callback=?',
        'http://fantasyfootballpundits.com/football/?category=In+The+News&format=json&callback=?',
        'http://fantasyfootballpundits.com/football/?category=Pundits+Team&format=json&callback=?',
        'http://fantasyfootballpundits.com/football/?category=Shrewd+Moves&format=json&callback=?',
        'http://fantasyfootballpundits.com/football/?category=Guest+Fantasy+Articles&format=json&callback=?'
    ];
    urls.forEach(function (u) {
        $.getJSON(u).done(function (data) {
            var current = data.items[0];
            if (current != null) {
                var post = '<li><a href="http://fantasyfootballpundits.com' + current.fullUrl + '"><img src= "' + current.assetUrl + '" alt ="' + current.filename + '"></a></li>';
                $('ul.slides').append(post);
            }
        });
    });
});

What other sliders would people recommend that can be used with dynamically loading images from. I need preferably a slider that will have better performance then fancy things. Flexslider isn't loading, it has a huge delay.

Im looking at this jcarousel http://sorgalla.com/jcarousel/. But not to sure.

any ideas or options for a more suitable slider would be great