var d = new Date();
var currentMonth = d.getMonth();
currentMonth = currentMonth + 1;

function getImage()
{

var randomVal = (Math.floor(Math.random()*4)) + 1; // value = 1 thru 5
var Img;
var season;

switch(currentMonth) {
  case 12:
  case 1:
  case 2:
    season = "winter";
    break;
  case 3:
  case 4:
  case 5:
    season = "spring";
    break;
  case 6:
  case 7:
  case 8:
    season = "summer";
    break;
  case 9:
  case 10:
  case 11:
    season = "fall";
    break;
}; //end switch

Img = "woodlots_" + season + randomVal + "_bkg.jpg";
Img = "images/" + Img;

  if (document.body) {
    document.body.style.backgroundImage = 'url(' + Img + ')';
  }

}