Here's all items with a custom/modified "head" display render thing, as of 1.21.10.
The "template" stuff is for multiple variants.

1.21.10\assets\minecraft\models\block\*.json

calibrated_sculk_sensor

faces the purple bit forwards
calibrated_sculk_sensor
calibrated_sculk_sensor2

        "head": {
            "rotation": [ 0, -180, 0 ],
            "translation": [ 0, 0, 0 ],
            "scale": [ 1, 1, 1 ]
        }

end_rod

unicorn
end_rod
end_rod2

        "head": {
            "rotation": [ -60, 0, 0 ],
            "translation": [ 0, 5, -9],
            "scale":[ 1, 1, 1]
        }

stairs

stairs
stairs2

        "head": {
            "rotation": [ 0, -90, 0 ],
            "translation": [ 0, 0, 0 ],
            "scale": [ 1, 1, 1 ]
        }

template_campfire

campfire doesn't actually have a model, but we can see what it would look like using vanilla tweak's 3d models resource pack.
possibly from 19w02a when campfires didn't have an item texture?
template_campfire
template_campfire2

        "head": {
            "translation": [ 0, 10.5, 0 ]
        }

campfire_off

i believe this is impossible to see, possibly left over from before we had soul campfires?

        "head": {
            "rotation": [ 0, 0, 0 ],
            "translation": [ 0, 10.5, 0 ],
            "scale":[ 1, 1, 1 ]
        }

template_custom_fence_gate

template_custom_fence_gate
template_custom_fence_gate2

        "head": {
            "translation": [0, -3, -6]
        }

template_fence_gate

        "head": {
            "rotation": [ 0, 0, 0 ],
            "translation": [ 0, -3, -6],
            "scale":[ 1, 1, 1]
        }

template_lightning_rod

template_lightning_rod
template_lightning_rod2

        "head": {
            "rotation": [ -180, 0, 0 ],
            "translation": [ 8.5, 4, 0 ]
        }

1.21.10\assets\minecraft\models\item\*.json

amethyst_bud

moved to front
amethyst_bud
amethyst_bud2
amethyst_bud3
amethyst_bud4
amethyst_bud5
amethyst_bud6

    "head": {
      "translation": [ 0, 14, -5 ]
    }

amethyst_cluster

amethyst_cluster
amethyst_cluster2

    "head": {
      "translation": [ 0, 14, -5 ]
    }

bone

bone in mouth
bone
bone2

        "head": {
            "rotation": [ 0, 0, -45 ],
            "translation": [ 0, -4.5, -6.5],
            "scale":[ 1, 1, 1 ]
        }

cod

fish slap
cod
cod2

        "head": {
            "rotation": [ 0, 90, -60 ],
            "translation": [ -7, -4, -7],
            "scale":[ 0.8, 0.8, 0.8]
        }

conduit

pointless, its hidden in the head
conduit
conduit2

        "head": {
            "rotation": [ 0, 180, 0 ],
            "translation": [ 0, 0, 0],
            "scale":[ 1, 1, 1]
        }

decorated_pot

pot on head
decorated_pot
decorated_pot2

        "head": {
            "rotation": [ 0, 180, 0 ],
            "translation": [ 0, 16, 0],
            "scale":[ 1.5, 1.5, 1.5 ]
        }

feather

feather pointing up
feather
feather2

        "head": {
            "rotation": [ 0, 0, 45 ],
            "translation": [ -1, 13, 7],
            "scale":[ 1, 1, 1]
        }

lead

monacle
lead
lead2

        "head": {
            "rotation": [ 0, 0, 0 ],
            "translation": [ 2.75, -2.75, -6.5],
            "scale":[ 0.8, 0.8, 0.8]
        }

spyglass_in_hand

funny spyglass
spyglass_in_hand
spyglass_in_hand2

        "head": {
            "rotation": [90, 0, 0],
            "translation": [0, 0, -16],
            "scale": [1.6, 1.6, 1.6]
        }

template_banner

banner on head
template_banner
template_banner2

        "head": {
            "rotation": [ 0, 180, 0 ],
            "translation": [ 0, 16, 7],
            "scale":[ 1.5, 1.5, 1.5 ]
        }

template_bed

template_bed
template_bed2

        "head": {
            "rotation": [ 0, 180, 0 ],
            "translation": [ 0, 10, -8 ],
            "scale": [ 1, 1, 1 ]
        }

template_chest

face chest forward
template_chest
template_chest2

        "head": {
            "rotation": [ 0, 180, 0 ],
            "translation": [ 0, 0, 0],
            "scale":[ 1, 1, 1]
        }

template_copper_golem_statue

copper statue facing forward, on head, flipped correctly
template_copper_golem_statue
template_copper_golem_statue2

       "head": {
          "rotation": [ 0, 180, 180 ],
          "translation": [ 0, 22.5, 0 ],
          "scale": [ 1, 1, 1 ]
      }

template_shulker_box

shulker box facing forward (basically pointless)
template_shulker_box
template_shulker_box2

        "head": {
            "rotation": [ 0, 180, 0 ],
            "translation": [ 0, 0, 0],
            "scale":[ 1, 1, 1]
        }