Your problem with the "sell" on this image is that the globe image you've composited in is first of all distorted out of aspect ration, then it's not clear if you're trying to go for a "planet in a garage lockup" concept, or a "poster of a planet" painted onto the wall. If i was the latter, then you'd need to fake some specular highlights and reveal a little of the wall texture. If it's the former then you want to watch your aspect ratio more closely (Keep the earth earth shaped) and perhaps use some of the foreground frame to occlude the composited image to make the obvious hard-edge less obvious. Hanging ivy, broken masonry, that sort of thing.