thank you , and also thanks for the CC , I think the lighter value was important to keep as it was to give it the contrast it has in the drapery as the original painting was composed , but I think your criticism is valid and that perhaps I should have used bigger clusters in some areas 

Nice work. At this tiny scale, I think the dithering is a bit too difficult to pull off without adding noise that can't properly communicate shape but you managed to create a good deal of depth. Personally I would have gone for a few bigger clusters here and there.