use the CCWIMAQVision class to create the image, then set the type to RGB, read the image file, and then attach the image object to the image viewer control.
image=m_CWIMAQVisionObj.CreateCWIMAQImage();
image.SetType(IMAQ_IMAGE_RGB);
m_CWIMAQVision1.ReadFile(image, m_strPath + "\\myimage.tif", COleVariant((long)32), vOptional);
m_CWIMAQViewerObj.Attach(image);