The photo layer is duplicated then G'MIC Artistic/Diffusion Tensors is run on the top layer. The top layer is then put into a layer mode.
For this one, I used Difference mode then adjusted levels on the bottom layer.
![Image](http://gimpchat.com/files/1812_PsychFantasy.png)
For this one, I used Grain Merge mode then reduced the opacity of the top layer.