Result

jQuery

$(".vimeo-thumb").each(function(){
        var id = $(this).data('vimeoid');
        //JSONを取得してIDを代入
        $.getJSON('http://www.vimeo.com/api/v2/video/' + id + '.json?callback=?', {format: "json"}, function(data) {
            //.vimeo***というclassのDOMに背景としてサムネイルを指定
            $('.vimeo' + id).css('background-image', 'url("' + data[0].thumbnail_medium + '")');
        });
    });

css

.vimeo-thumb {
    background: #fff url(foo.gif)
}​

html

<img alt="Vimeo" class="vimeo-thumb vimeovimeoの動画ID" data-vimeoid="vimeoの動画ID" src="foo.gif">

via

https://forrst.com/posts/Vimeo_thumbnails_dynamically_with_Javascript-w5j