This is really easy and I think it makes a nice effect.



Step 1

Select your gradient tool, Make sure it isnt hiding under the paint bucket tool.

Make sure that you have these options applied.



Step 2

First make sure you have white background and press D to reset the color.

And go CRAZY with the gradient tool, go all over the picture 10-20 times until you have something like this.



Step 3

Select your wave tool, it is in Filter / Distort / Wave.



Now press randomize



--- I got this ---



Step 4

Duplicate the layer. Right click on the layer and press duplicate, then ok. Double click on the background layer and press ok. It will be renamed layer 0.

Step 5

With the topmost layer selected go to Edit > Transform > Flip Horizontal and change the top layers blending option to lighten. The blending mode options are located on the top of the layers pallete.

Step 6

Now you can mess around with the image and do what you want with it.
Try coloring each layer different colors and so on.

Have fun!!!