FBPhotoZoom is a Safari Extension that zooms photo thumbnails on hover. It is based upon the Chrome extension, though it is a complete rewrite.
To install and use this extension, Safari Extensions must be enabled. To do this, go to Safari > Preferences > Advanced and check "Show Develop menu in menu bar". Once the Develop menu is active, click Develop > Enable Extensions. You can then view your extensions in Safari > Preferences > Extensions.
Once Extensions are enabled, download the packaged extension here.
The full source is here, because I imagine that there are many improvements that can be made. For example, I'm sure I missed some photo selectors. If there's a better way, I invite you to contribute -- just clone, edit and make a pull request. Enjoy!
Logan Leger email@example.com