I remember the old alchemy of making a double exposure too ... fun stuff!
That one is actually just a reflection. One of the things I like about digital photography is that taking a pix is essentially free and the results are instant. You think something looks interesting? Take a shot of it.
So we're in Paris, walking along the Champs-Elysses, and I saw the mannequen heads and thought them kinda odd looking. Snap. I didn't even notice the trees in the reflection until I looked at the result, and in retrospect, they make the photo more interesting.
I'm a landscape guy myself, but you never know what you'll see, even in a busy city. I took this picture of a guy cleaning a window display moments after the mannequin pix ... thought it was kinda amusing. lol