Minecraft wiki entry for Development_versions, associated text: Item Icon Component
Items now have an easy way to set the icon for an item for displaying in the user interface
Component Variables
texture: Full path to icon image to use as item's icon. No default
frame: Molang script to be executed at runtime to determine the icon's current frame. Can be a constant, defaults to: 0
legacy_texture_id: The name of the texture used on legacy items. No default
legacy_frame: Molang script to be executed at runtime to determine the icon's current frame. Can be a constant, defaults to: 0