There is a relatively small number of sculptures and most fall into categories which are easy to identify but more difficult (for a layman, at least) to name. As an initial draft the categories are:
angular, rounded, granite, brass, planar, other / singular, and no image.
There is some overlap, for example with brass and granite, but it is a reasonable starting point. There are probably subjective groupings within the categories that will guide the arrangement.
