Federico Viticci writing for MacStories:
A batch renaming option has been added to the Finder in Yosemite: if you need to rename multiple files at once, select them, then choose “Rename [x] Items…” from the contextual menu. This will open a modal dialog with three options to batch rename files: Replace Text, Add Text, and Format.
This is an excellent new feature that I probably would have glanced over without noticing if it weren’t pointed out to me. It won’t replace the advanced renaming capabilities contained within Forklift, but it will certainly save me a lot of time with small, quick tasks.
Be sure to follow through and check out all the other little OS X Yosemite tidbits Federico dug up over on MacStories.