Watermarking - Your sensitive images should be watermarked before sending to someone to protect against exploitation by unkind or immoral people.
PhotoPenguin App - PhotoPenguin is a completely free batch photo editor with support for cropping, resizing, adding watermarks, and converting photos to other formats. It works on the user's device, using the capabilities of modern browsers.
maWatermarker - A great tool to watermark your images.
Batch Image Resizer - Resize, crop, shrink, flip, exif-rotate, convert, enhance, process multiple pictures and photos with professional software! 120+ Actions, 30+ Image Formats
PreviewMaker - PreviewMaker helps you to put watermarks on a lot of photos.
ImBatch - ImBatch is a batch image processor with a nice graphical user interface.