Right - there's a lot of wasted space in the cupboard. How about one or two of those metal shelf inserts and putting the spices into little baskets. Mine are roughly arranged in groups: herbs in one, baking spices in another, general spices in another, curry spices in another.
Or you could hang a large spice rack on the inside of the door. There was one poster who had magnetic paint on the inside of the cupboard door and metal containers stuck to it by the lids. Alternatively, if you have the drawer space, there are various drawer inserts.