A little bit of auto-thread-necromancy.
I've updated the script at the plugin registry to (optionally) restrict the number of files that can get backed up (the default is 5). Changing the value requires a modification to the script code, as explained in the description there.
Also, the old script only used the filename, so file.jpg and file.png open in the same directory would back up to the same filename. how the extension is also included in the filename.

As a note, I rely on this alot when working with big files in gimp, and it is just an Alt-F,B away...

-Rob A>