What I didn't realise is that you can use the Path Selection Tool (the dark arrow in the toolbox) which will select entire shapes, then Ctrl+C and Ctrl+V the selection into another shape layer. When you paste you will notice in the tool bar that the Combine button will become active and clicking this will join the shapes into one shape. You can also make negative joins which is very useful to cut bits out existing shapes.
As for the picture I found it was a bit dull, so I added the hand coming at the viewer to give it some drama. I also I tried to vary the line weights to mimic the kind of brush inking style that used to be popular in pulp comics.