I recently discovered the American Antiquarian Society’s Farber Gravestone Collection, with 13,500+ images of lettering, skulls, rubbings, and generally great gravestone graphics. Better yet, it's all methodically cataloged and browsable by theme, location, date, stone carver, etc.

Do yourself a favor and set aside some time to browse through it all.
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https://farber.davidrumsey.com/luna/servlet
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There’s also an introductory essay about the collection with lots of background info (PDF):
https://www.davidrumsey.com/farber/Early%20American%20Gravestones.pdf