Cool picture :D I really like your use of color :)
I think it is an alien doing spelunking. Yet I wonder what is at the bottom of his ship. Probably his legs Flintstone-esque 
The shading is nice, but I don't understand what the subject matter is. Is this an alien crushing a white and green monster with his ship?
Haha, it may be unclear unless you've played the game Spelunky. These little aliens are in it and they shoot beams from the bottom of their UFO, the white/green stuff at the bottom is that.