Making a watermark for images is very easy to do , basically you just take your text or logo , whatever you want to be your watermark and turn the transparency down ( I use 20-30% ) , once you have your transparent logo/text you just overlay that over your image and flatten the image if needed.

If you use a watermark , and someone steals your image its hard for them to claim it isn't your image , since your name is on it. You want your watermark in the center of the image so it cannot be cropped out.

If you are using watermarks for your own website , and do not want every chip to have a watermark over it , you could use a mouse-over watermark , so only when the persons mouse hovers over your image , the watermark shows. If they try to copy the image they will get the copy WITH the watermark on. If you would like to see this demonstrated just let me know and ill toss one up onto my website. ( This would not prevent the image from being stolen via a screen shot tho )

If you want a water mark or something else made dont be shy about asking , they only take moments to make.