You could try adding some height to the larger piece just off centre.
Leave the larger piece where it is and add the smaller piece on top. So take the small piece off centre right and place it on top of the larger piece off centre left.
If you can move the white rock formation slightly toward the back if possible once the small is on the large.
That might look cool and give you a little more scope to add something small on the right side where the smaller rock was.
Jon