There is stuff in your background that you can almost but not quite see and that is to me very distracting. There also is no true black which looks kind of wierd for this type of shot.
TC
Well the ground looks beliavable as a moon, so does the rock but the sky on the other hand is too gray (as in not black) for it to be really believable. If I had done this image I would have gone out and taken star sky shot´s and used that as the sky, would have lead this image to be much more aesthetically pleasing. Also the blur on the rocks close to the horizon is also giving it away, this would have infinity focus if it were a real photograph from the moon or the floating rock would also be blurry. Nice effort, just needs better execution and your all set :)
Cute idea! Nicely done. Colours are a little washed out though that's not such an issue given content but I think a touch more saturation would be good.