var imagenumber = 9 ; //Anzahl der Grafiken
var randomnumber = Math.random();


var rand1 = Math.round( (imagenumber-1) * randomnumber) + 1;


images = new Array
images[1] = "url('/fileadmin/wave/images/header/waveheader1.jpg')"
;
images[2] = "url('/fileadmin/wave/images/header/waveheader2.jpg')"
;
images[3] = "url('/fileadmin/wave/images/header/waveheader3.jpg')"
;
images[4] = "url('/fileadmin/wave/images/header/waveheader4.jpg')"
;
images[5] = "url('/fileadmin/wave/images/header/waveheader5.jpg')"
;
images[6] = "url('/fileadmin/wave/images/header/waveheader6.jpg')"
;
images[7] = "url('/fileadmin/wave/images/header/waveheader7.jpg')"
;
images[8] = "url('/fileadmin/wave/images/header/waveheader8.jpg')"
;
images[9] = "url('/fileadmin/wave/images/header/waveheader9.jpg')"
;

var image = images[rand1] 

//document.getElementById("main_menu_container").style.backgroundImage = image;