Try this
uMark Lite
Their blurb...
uMark Lite is a FREE batch image watermarking tool
With uMark Lite you can -
> Add text or your company logo as watermark to any image
> Customize the font, color, shadow, transparency of the watermark
> Position the mark on 9 different places on the image
> See the preview of the watermark
> Process up to 50 images at a time
* uMark can process images of type BMP, JPG and GIF
* Watermark will be added to the image without any loss in quality
* uMark is amazingly fast. You can watermark Hundreds of images in minutes