Now on the Internet Archive are back issues of Markers, the annual journal of the Association for Gravestone Studies,with definitive illustrated articles on cemetery and gravemarker topics as well as an extensive annual international bibliography of recent scholarship.
Volume 1 (1979/80) to XXV (2008) are available, with more recent volumes only available to Association members.
There is a subject index up to volume XII at https://www.gravestonestudies.org/markers.htm
Although the bulk of the articles are US oriented there are a few relating to Canada (BC, Ontario, Nova Scotia), England, Ireland and Scotland.
This could be a useful reference if you find yourself, say, wondering about unusual gravestone iconography.