I love McGuinness Flint (Happy Birthday Ruthy Baby is a classic, and the band has been woefully under-recognized!), but your example doesn't fit the thread -- pall bearers and a casket, but no tombstone! Here's a cover which DOES qualify, and a tip o' the hat to SHF member Pim for posting it in another thread, as I was otherwise unfamiliar with it: Bass Communion
The Hellacopters - Rock & Roll Is Dead. Some copies of the US pic disc version had the tombstone motif.
I went to a friend's house yesterday, he showed me his most recent purchase, and what do ya know -- tombstones on the album art, specifically the gatefold! The Dead Daisies Holy Ground
Apologies if some mentioned Beggars Banquet 1973 The Rolling Stones L'age D'or Des Series (Mural painted by Brian Jones on his wall) Led Zeppelin II 199? Russian Pressing (rear cover) J.B. Lenoir His actual tombstone Unsure of title or year of release.
One of the earliest Christian prog rock groups of the '70s was Agape; this was the cover of their 2nd album. Victims of Tradition - Agape (1972)
As the OP of this thread, I can assure you, ADTL, no one has mentioned the examples you came up with (unlike the examples that SHF member mother mentioned). Your last example combined with the others quoted in this post constitute a thread-within-a-thread of artists whose tombstone appears on the cover of their own album. Here's the one you found: (This is really more of a grave marker than a tombstone, but I say it still counts. Seeing this is probably why John Mayall paid money out of his own pocket to have a tombstone made for Lenoir.)
Landon Spradlin - "No More Blue Mondays". Appropriate, since he went to Mardi Gras last year to prove that COVID was no big deal, and then died from it a month later.