How to insert on icon/image in ListGridField

[Rauel]

I'm trying to inser one icon on my list but I can not, I looked at the showcase example of the image( http://www.smartclient.com/smartgwt/showcase/ grid_datatypes_image )

			ListGridField colunaRelAprovado = FabricaComponentes
					.criaListGridField(new ConfigListGridField().setNome(Constantes.FIELD_REL_APROVADO));
			//colunaRelAprovado.setAlign(Alignment.CENTER);
			//colunaRelAprovado.setType(ListGridFieldType.IMAGE);
			colunaRelAprovado.setImageURLPrefix("images/correct_16x16");
			colunaRelAprovado.setImageURLSuffix(".png");

any idea?