Looks nice, but it'll work better if you remove the greenscreen a tat better, and add shadows to the little dudes..
Adding shadows is usually very simple, but adds alot of realism. just take the footage your editing in, colourgrade it to something dark and desaturated to create a shadowy look, usually i start 80% darker with 80% desaturation and 80% opacity, and then tweak till it looks just like the other shadows in the scene, but I do that just because I like the 80's. Oh wait i dont, moving on:
To place it: flip the image vertically, and skew the image horizontally untill you get the desired shadow angle. You could stretch the final image to get the desired shadow length.