Who placed the item. Drives the ownership chrome (chips / violet vs slate-amber).
Stable item id (e.g. sticky-3) — referenced by connectors, deltas and agent tools.
OptionalUrlOptionalWWidth in px; defaults to WHITEBOARD_DEFAULTS.ImageW.
Render order (higher renders on top). Assigned by the engine.
A pasted / inserted image card.
Urlis a runtime object URL (not persisted as pixels).