Create new 500x500 transparent document.
Filter->Render->Clouds
Filter->Stylize->Find edges
Image->Adjustements->Invert
http://img8.echo.cx/img8/8248/more11go.jpg
Image->Adjutement->Hue/Saturation use these settings:
Colorize-checked
Hue: 190
Saturation: 100
Lightness: +15
Now zoom out image (ctrl-)
http://img8.echo.cx/img8/5977/more28hw.jpg
Edit->Transform->Perspective
If your layer is locked you should double click it on layers palete to unlock it.
Drag bottom corners like this:
http://img8.echo.cx/img8/9440/more36fm.jpg
New layer.
Filter->Render->Clouds
Filter->Stylize->Find Edges
Image->Adjustements->Invert
Image->Adjustements->Brightness/Contrast
Use those settings:
Brightness: 0
Contrast: +90
Now, edit->transform->perspective just like before.
http://img8.echo.cx/img8/7137/more46jg.jpg
Set blending mode to lighten, screen, or exclusion, whatever you like.
Final results:
http://img8.echo.cx/img8/2481/more53zi.jpg
or
http://img160.echo.cx/img160/9324/more64lm.jpg