<imgpkg src="URL">
which could be something like a tar file with all the inlined images in it.
references on the page would be stay the same (i.e. <img src="URL.gif">)
However the browser could (if the tag is recognized) go retrieve the package,
and grab all the inlined images in it in one shot, should improve performance
dramatically on pages with lots of inlined images.
-Crh