Watermarks are a smart way to identify your pictures, add some copyright information to them and also discourage people from using them improperly.
With WinWatermark you can easily add those watermarks to your pictures before publishing them online. The program supports working with a single image as well as processing photos in batches.
Watermarks can be either small graphics or text snippets, both of them with many customization options as for their transparency level, location on the picture, size and other elements.
Besides watermarks, WinWatermark also enables you to add a frame to your photos, again just with one picture or working with many of them at the same time.
Frames also have a wide range of configuration options to make them look just the way you want.
WinWatermark can save resulting images in different graphic formats with adjustable quality values.
Also, I specially liked the possibility to save watermarks for later use.
If you're looking for a complete watermark application with which to identify your pictures, WinWatermark is probably one of the best ones you can find.