Learn to apply the Warp Tool effectively and a few other tricks to make smoke look like a skull. This technique has a variety of outcomes and works well with water, clouds and a whole bunch of other stuff. This is probably more for intermediate users, as I guide you through the process well, but not every Warp Grid point handle move. Check out the tutorial below: http://creativelayer.blogspot.com/2010/08/photoshop-eraser-tool-clone-stamp-tool.html