public class DrawingClientData 

using( var workbook = Workbook.Create( "AddPicture.xlsx" ) ) 
  { 
    // Gets the first Worksheet; a Workbook always contains at least 1 Worksheet. 
    var worksheet = workbook.Worksheets[ 0 ]; 

    // Adds a Picture with its top left corner located at the intersection of the 15th Row and 1st Column. 
    var streamPicture = worksheet.Pictures.Add( "balloon.jpg", 14, 0 ); 

    // Locks the Picture when the Worksheet is protected. 
    streamPicture.DrawingClientData.Locked = true; 

    // Saves Workbook to disk; 
    workbook.Save(); 
  }