If there are semi-transparent pixels in the hat texture of a skull on the head of an Armor Stand, they will block the view of a block on the head of another Armor Stand. I'm not sure if this affects skulls on the heads of other Armor Stands or whether this can be extended to any entity. Do look into it.

Steps to reproduce:

1. Place 2 command blocks (impulse and chain) in negative X direction
2. Insert the following commands in order (impulse block first):

   summon armor_stand ~ ~1.25 ~ {Small:1b,NoGravity:1b,ArmorItems:[{},{},{},{id:"skull",Count:1b,Damage:3,tag:{SkullOwner:{Id:"6b515abd-7537-325d-833f-c6f1aebd022d",Properties:{textures:[{Value:"eyJ0aW1lc3RhbXAiOjE0NjczMTI5OTc0MjYsInByb2ZpbGVJZCI6Ijc3NmZmMWRkZjhlNzQ3ZTRhNjQxMmRlYTA1YmRjNzIwIiwicHJvZmlsZU5hbWUiOiJBRkthdmVtYW4iLCJ0ZXh0dXJlcyI6eyJTS0lOIjp7InVybCI6Imh0dHA6Ly90ZXh0dXJlcy5taW5lY3JhZnQubmV0L3RleHR1cmUvNjdkOGNhMzdkZjM0M2Q2Y2VjM2U1MGYwNTk4YjI1NDJlMDc4ZGU1ZWY1MjdiMWJkY2EzNzE2ODFjNzMzYWMzZiJ9fX0="}]}}}}],Invisible:1b}
   

   summon armor_stand ~1 ~1.25 ~ {Small:1b,NoGravity:1b,ArmorItems:[{},{},{},{id:"nether_wart_block",Count:1b}],Invisible:1b}
   

3. Activate the impulse block. The Armor Stands should be created.
4. Examine the structure closely. Even though the Nether Wart Block should be visible through the blue pixels, it is not.