In the top drawing i've put the eyes in, just squares at the moment. and i've draw a line accros the top of the head, following the curve of the sphere again. this will be used to place the ears.

The bottom sketch has had the ears put in, flopped over for the added puppy look.
I've added a curve at the top of the eyes, flowing down to the muzzle. i prefer this look but for a more cartoon look leave this off.
the mouth has also been extended into a smile.