1) open a new image any size you want
2) set your colours to default by pressing "D" on your keyboard
3) Filter > Render > Clouds
4) Filter > Liquify and mess around a bit
5) press ctrl+L to bring up the level box and click the button "auto"
6) Filter > Stylize > Find Edges
7) If you like this image, you keep it this way, or else you can invert (ctrl+I)
8 ) add some colour by pressing ctrl+U and click "colourize" :thumbsup:
Not inverted:

Inverted:

Thunder-Eagle B)