I was not able to show task notes icon, as appears in MS Project. how can i insert a picture in a grid cell?

Answer

You need to assign an imagelist with your icons to Gantt.GridProperties.ImageList.

Every cell has a CellLayout that controls the rendering properties of the cell. You can set the CellLayout.ImageIndex_Select and CellLayout.ImageIndex_UnSelect to an imagelist index. These values will be used when the cell is selected and not selected respectivly.