var imageArray = [];
imageArray[0] = 'image_01.jpg';
imageArray[2] = 'image_02.jpg';
imageArray[3] = 'image_06.jpg';
imageArray[4] = 'image_03.jpg';
imageArray[6] = 'image_04.jpg';
imageArray[7] = 'image_01.jpg';
imageArray[5] = 'image_05.jpg';
imageArray[1] = 'image_06.jpg';
imageArray[8] = 'image_07.jpg';
imageArray[9] = 'image_01.jpg';
imageArray[10] = 'image_08.jpg';

            var imageNumber = 11;
            var randomnumber=Math.floor(Math.random()*11);
            var file = imageArray[randomnumber];