PhotoRenamer is a free tool which enables the renaming of multiple digital images from cryptic DCS014752.jpg-type names to something more consistent and meaningful.
The program opens with an Explorer-like tree. Choose the folder containing your images and thumbnails are displayed, eventually. The process seemed much slower than with Explorer, and there doesn't seem to be any cache (display takes a while every time you select a folder, not just the first time).
Files are renamed by using a custom mask. This defaults to %Y-%m-%d %H-%M-%S, which effectively replaces the existing name with the image date and time, using dashes as a separator: "2017-2-23 16-23-06.jpg".
The program comes with four similar masks, and you can edit these or create your own, optionally using EXIF or IPTC tags. Select any mask and the thumbnail view displays both the current file name and the new one, a handy preview of what Photo Renamer is going to do.
By default files are renamed in the folder where they're currently located, but there are two unusual alternatives. "Backup Rename" copies your selected files to a backup folder and renames the files in the source, while "Target Rename" copes the files to a backup folder with the new name.
Whatever your renaming choices, there's always the chance of creating new duplicate files. PhotoRenamer handles this automatically by adding -001, -002-type suffixes, and this can also be customised if necessary.
PhotoRenamer has a lot of batch-renaming power and some unusual pluses, but it's not always easy to use. Expect to spend a while with the help files and video tutorials before you fully understand your options.