an image, you don't need a place holder, the image will hold that place. If you are talking about a background image, you can just make its parent container the size of the image. That will act as a placeholder. The only benefit I might see is that you can put a transparent image as a place holder with an ALT tag to describe the background image that can be found there. Other than that, I can't think of a good reason.
could you please advise me when we should use image holder for placing an picture into a webpage. what are the benefits of using image holders?