The only problem I see with this is the source code for 
each mirrored page will still have the external ??? image 
as the background. Right now, I am having to manually edit 
each and every page to reflect the proper image which is 
stored locally.

However, this is tiresome and cumbersome. Is there some 
other way? Aside from this one background image, the site 
downloads fine.

And no, it's not called by any means, regularly the image 
is loaded by HTTP (like any other one).