Can get some really great effects by mapping a fractal image to a photograph. The more contrast in your photograph the better. The tutorial below, only covers the absolute basics of doing this. It’s recommended to play around a lot to get the desired effect. Some other things you can try, are to blur the mask image before you save it. Also once you’ve applied the image to your photo. You can use the brush (set foreground colour to black and very low opacity) to bring parts of the original image back where you don’t want the fractal to show. In the case of the example, that might be the hair.
It’s important to make sure the images are the same size, so rather than complicate the main tutorial with that, I’ve done a smaller tutorial below on how to match image sizes.