I sometimes needs to rename bunches of files. I typically use the command line tool mmv, which can do things like this:
mmv 'IMG_*.JPG' 'img_#1.jpg'
It would, however, be nice to have a GNOME tool to do the same thing. It would be nice to have a preview of what's going to happen, and perhaps have ways of remembering particular renaming patterns, so that they're easy to use if I need them repeatedly.