you can do it with TCAD's inspector.See BkBitmap property,it can load a bitmap form a file and BkBitmapMode property,it can change bitmap's show style.

Also,you can do it by code.see it.

Code example:

procedure TMainFrm.Button1Click(Sender: TObject); 
var 
  mBitmap:TBitmap; 
begin 
  mBitmap:=TBitmap.Create; 
  mBitmap.LoadFromFile('xpatag.bmp'); 
  MyCAD1.BkBitmap:=mBitmap; 
  MyCAD1.BkBitmapMode:=Center; 
  mBitmap.Free; 
end; ;