Looks REALLY nice.
Maybe crop it a bit; there's dead space along the bottom of the picture where nothing is happening, and since the aliens are the focus of the pic anyway ... why not bring us closer to them and the action? Or scatter the debris farther out into the room to make use of the space?
Alternatively, you could add more drama and a layer of depth to the image by putting another alien up closer to the camera -- sort of like he's barking orders to the horde spilling in behind him.
Maybe, by way of visually explaining how the hole was made, you could add some fire and smoke behind the aliens from the just-detonated bomb. Perhaps obscure the aliens partially in the smoke as they emerge, adding some menace and mystery.
These are more suggestions than critiques; the actual image works quite nicely all by itself. :)