title: loading dynamically discovered images in the background
body: <p>The mySql database contains the images that my page needs.   They are not known at script load time.
  When I discover the image names, I am sucessfully preloading the needed small thumbnails, but the bigger image that is needed later paints like a snail.   I need to figure out how to start the downlaod of the big images while the page is rendering the small ones.   This should by an async operation as I do not want to block my page.  Can someone suggest how to get the big images loaded before they are needed?</p>