It's possible to make Player Heads the size of full blocks by putting them into an item display,
then changing the scale of the item display to 2 on every axis.
This is useful because Player Heads are the only block that you can change the texture of without a resource pack,
as the texture is stored in the item components as one (or both) of the following:
- The username of the player whose skin should be used. (as seen in the example command)
- A Base64-encoded link to a skin texture on Minecraft's servers.