cheers for that ive already had a play around with it before i saw this message, but i can still change the lighting :) here is what it looks like with the detail
Its a good start, but you should try avoiding the "banding" you are getting. Use a different brush, or use bigger strokes. Also try to define the terminator a bit more. Also try to add reflected light in the shadow side. The falloff in the lit side doesn't seem to realistic, spread it out more evenly.