Order by    
SELECT yourRef, propNameEn, propPrice, propBathroom, propBedSingle, propBedDouble, propHouseM2, propLandM2, propJardinM2, propBalconM2, propTerrazaM2, medium, propType, propParking, propGaraje, id_unico, propStatus FROM propiedades INNER JOIN imagenes_propiedades ON(imagenes_propiedades.ref = propiedades.id_unico) WHERE 1 = 1 AND imagenes_propiedades.orden = '1' GROUP BY yourRef ORDER BY fechaPublicacion DESC limit 9, 9