Yea, outer spots are kinda useless. Maybe should I have made more rocks instead. However, this was my the first image where I used dithering on purpose.

Good job! I'd try to remove as much dithering as possible though.

I wouldn't have imagined you could do so much with just three colors. Nice work. 

You are beginning to understand how highlights and shadows work, nicely done.

You are doing great trying new things and experimenting. kutgw.