RewriteEngine On
RewriteCond %{REQUEST_URI} \.(jpg|jpeg|gif|png)$ [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .*$ /no_picture.png [L]

Let's break it down as to what each line means.

RewriteCond %{REQUEST_URI} \.(jpg|jpeg|gif|png)$ [NC]

Check to see if the requested file is of a file extension in the parentheses (). In this case, we're testing to see if the file name ends in either .jpg, .jpeg, .gif or .png

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

Check that the file is not there and it's also not a directory.

RewriteRule .*$ /no_picture.png [L]

If a requested resource/file passes all those tests, then it's an image that does not exist. So serve back the image of no_picture.png to the browser. This will keep the filename. If you want to redirect to the no_picture.png filename, change [L] to [R]

Refresh document every 300 seconds using HTML Meta tag add this inside the head tag of the page

 <meta http-equiv="refresh" content="300">

Or using Java Script:

            setInterval(function() {
                  window.location.reload();
                }, 300000);