I believe that you need to protect your online images either self hosted or by third parties like Flickr or ImageShack. Of course you can do this with your favorite image editor and add your copyrights note from there.
PickMarkr is a free online tool to add watermark to your images or photos. There 3 steps only.
First, you just need to upload them (up to 5 images) and select the output image size. Second, insert a text for your copyrights (other message is welcome) and select it’s position. Third, after submitting for final process, you can download or upload it to your flickr account.
Other type of watermark are available. You can use your logo as image watermark. It’s also can be tiled.
Try it your self. Here is a sample for you.