var mypics = new Array();
mypics[0] = new Image(800,150);
mypics[1] = new Image(800,150);
mypics[2] = new Image(800,150); //Image()の()内の数字は画像の幅・高さ（ピクセル数）
mypics[3] = new Image(800,150); // 画像の数に応じて増やす
mypics[0].src = "http://blog-imgs-18.fc2.com/p/o/l/polukai/F300415photo_0.jpg"; // 表示したい画像のパスを指定
mypics[1].src = "http://blog-imgs-18.fc2.com/p/o/l/polukai/F300415photo_1.jpg";
mypics[2].src = "http://blog-imgs-18.fc2.com/p/o/l/polukai/F300415photo_2.jpg";
mypics[3].src = "http://blog-imgs-18.fc2.com/p/o/l/polukai/F300415photo_3.jpg";

function chgmypics() {
   if (document.getElementById("pic")) {
      var elem = document.getElementById("pic");
   }
   else return false;
   if (elem.i == undefined) { elem.i = 0; }
   elem.src = mypics[elem.i].src;
   elem.i = (elem.i==mypics.length-1) ? 0 : elem.i+1;
   elem.chg = setTimeout("chgmypics()",5000); // 画像を切り替える間隔をミリ秒単位で指定（ここでは5000ミリ秒＝5秒）
}
window.onload = chgmypics;