The recently mentioned mirror site has the discussions on that script. It looks like the script has a few issues and some users suggested an alternative: http://userscripts-mirror.org/scripts/discuss/48293.html (I haven't tried any of them myself)
This script doesn't have the exact functionality you're looking for but it's pretty close.
The dev is very active, you could ask him to add your feature.
https://greasyfork.org/scripts/404-mouseover-popup-image-viewer
Google Images Direct Link
I see nobody has posted a script for Google Images. I have one that I like that is created by 'Dwoo' but I couldn't find any contact information about him anywhere.
I want the script to be improved since clicking the link on the bottom part of the picture doesn't work anymore. It used to be able to take you to the page, now it opens a Google Images dialogue.
The script is attached below.