Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.
PhotoBulk - PhotoBulk is a bulk image editor for Mac that was created for the best experience of batch editing. With this image editing software for macOS you can add watermarks, optimize and resize pictures, convert images or rename photos in bulk.
Batch Image Processor 2010 - Batch-process & create web gallery of images
IrfanView - IrfanView ... one of the most popular viewers worldwide.