Mobgriefing being off still allows creepers to destroy paintings. I tried many similar items and blocks and it seems to only be paintings.
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fezemerald
[Mojang] Mega_Spud (Jay)
Paintings, armour stands, leash knots etc can be damaged by mobs such as creepers, wither.
Mobs mentioned in MC-1673
creepers, withers, skeletons, strays, shulkers, ghasts and snowmen.
[Mod] Celesian
Fixed in a earlier version
migrated
Paintings are entities. WAI i think