A monumental mason just like any other type of masonry will have to have some means of storage for the material ie stone. This can either have a seperate space like a warehouse for this and could act as like a catalouge for people to come and pick their favourite stone or there could be one giant space in the workshop to facilitate all the needs. The storage could be left outside as the stones are not the type of material that cant withstand the elements so the stone/ tombstone heads could be left outside, this is common for most monumental masons as they traditional masons have smaller workshops mainly for 1/2 people.