[LearningCoder]

Maybe changing the function to something like this:

var currentImgNumber = 1;
var numberOfImages = 3;

function switchImage(){
   currentImgNumber++;
   document.body.style.background = 'url(images/AdvertImage' + currentImgNumber + '.jpg)';
   if(currentImgNumber == numberOfImages){
       currentImgNumber = 0;
   }
}

Set your additional attributes for the image just like you would do in the css like no repeats x+y etc. You can just add to that statement your other declarations.

Regards,

LC.