Here is something all us Mac users can use. PicMark 2.2 is a free application for Mac which helps you to process images. It can automatically apply watermarks to images and also helps the user to create thumbnails. One can also include in some basic editing as its capable of rotating, flipping, adjusting the color of, drawing a border around and drawing shadows behind hundreds of pictures in just a few minutes.

Download PicMark from the Digital Calamity website.

http://digitalcalamity.org/software/applications/picmark/