Picture pict=workSheet.Pictures("pictureName") as Picture;//workSheet is object of excel sheet
pict.CopyPicture(XlPictureAppearance.xlScreen, XlCopyPictureFormat.xlBitmap);//Copy to clipboard

//Get from clipboard
if (Clipboard.ContainsImage()){
Image img=Clipboard.GetImage();                    
pictureBox.Image = img;
}