By left clicking over an image area and selecting properties you will see the url address of that image. If you put the url in the address bar it will automatically display an image that is smaller than the original if it is a large image.  Bring your cursor to the lower right corner. This is where the enlarge button is located.  It may take a few seconds to appear and you may need to hover over the area for the for the button to show up.  Buy clicking the button the largest  version of the image will appear.  The download size is usually, but not always  the largest image.    

The image in this example is stored at http://static.flickr.com/62/195021271_e69018b995.jpg this link will bring you to the medium sized image used here.

As an example the  try this image : http://static.flickr.com/74/194974414_295f198d6a_o.jpg which is an large image that will automatically give you a smaller screen image.  Find the button and click to enlarge.  This comes in extremely useful when checking out satellite and space images.  as well as some of the higher detailed images that I will submit in the future.