What is the cost of this? What if the first image does not download from the web server in time? It seems like it will halt the page rendering until it gets the

What is the cost of this? What if the first image does not download from the web server in time? It seems like it will halt the page rendering until it gets the correct sequence. Personally, it makes sense to have the page loading, even if it is out of order and not ideal. It indicates to the user something is happening and the user tends to be more patient.