It is well suited for the position you have chosen to place the clock as the sweeping brush strokes on the original Mona Lisa image create a path directly to it. The addition of the flags along the dress are a nice touch too. Just wish you had worked with a much larger source image such as this Mona Lisa so that you could work with the textures of the original canvas.
C00per has good points. Love the composition, but I would also extend the London architecture to the right side behind Mona's back.