NameChanger is exactly what its name implies: a program to help you rename files on your Mac. This application might prove to be of good use when organizing your photo collection and wish to rename a large amount of pictures to fit a certain profile.
All you need to do is to import the files you wish to rename, choose the renaming method (for example, replace a word in the filename with another term), and click the "Rename" button. The application will immediately apply the necessary changes, without slowing down the performance of your system.
Furthermore, the program comes with a built-in image browser which allows you to preview the imported images before renaming them. You also have access to options to save and load renaming profiles for later.
The only thing I'd add to this utility would be an option to undo file renaming tasks. Many apps of its kind provide you with this feature.
Briefly, you should definitely give this program a try if you're looking for an easy and quick way to batch rename files on your Mac. Not to mention that you don't have to pay a buck to use it on your computer.