var i = 1;

function change_img() {

    if (i == 3) {
        i = 1

    } else {
        i = i + 1;
    }  
   
   $("img#gimg").fadeOut(2000, function() {
   $(this).attr("src","img/restaurace"+i+".jpg");
   if (this.complete) $(this).fadeIn(2000);
   });
   $("div.gmain").css("background-image", "url(../img/restaurace"+i+".jpg)");
  
}

setInterval("change_img()",4000);