"My best advice (which you won't like) is 'get over it'."
The economic loss from a stolen image from a website is likely very low to nothing. The person stealing it probably would never pay for it anyway. No lost sale. There isn't much the person can do with it commercially either, so he won't make a bundle off of your work. Anyone who wants to use the image for a big project (ad, poster, wallpaper, etc.) will just buy it.
The publicity of having your images out there is far better.