Check out some of my other posters here.
Side-note: bad perspective can be distracting, so I fixed the lollipop issue on the left. I had created the house and surroundings using free vector candy images, in the process of copying and pasting the images, I must have forgotten to scale down.
The change in lighting and color really changes the tone of the design. The clouds also give more interest to the top portion of the poster as opposed to a bland gradient.
It has been said that designers are forever critiquing their work during the process and long after it is done. I am no exception to this general rule.