Yeah see what you mean about it being cartoony, maybe it was the stress of a commission?
I think the ears need more work done, they don't look hairy like ears should. Also it hasn't got any whiskers, and the muzzle is very clear cut and rounded, they're normally a bit lumpy bumpy. Good job on the eye :)
Can we maybe have a reference picture? That might help us see things you haven't (I always need a second pair of eyes, especially after looking at the drawing for ages!)
Edit - Also the bit could do with some shading