Setting this property checks the current value of the TableCell.RenderObject property. If it is a RenderImage, the value is assigned to that object's RenderImage.Image.
Otherwise, a new RenderImage initialized with value is created and assigned to TableCell.RenderObject. Note that properties from the old TableCell.RenderObject are copied to the newly created RenderImage using the RenderObject.AssignFrom method. In particular, this copies the style from the old object to the new one.
Getting this property returns RenderImage.Image of RenderImage assigned to the TableCell.RenderObject on the current cell, or null if the current value of TableCell.RenderObject is not a RenderImage.