How can I create a custom page for this too many connections error page because I know it's because my server is overloaded? I wanted to show a custom error page instead of this when my website is overloaded by traffic.
Check out the source of
dead_db() which powers the message.
You'll see that you can create a file
db-error.php in your WP content directory (which by default is
/wp-content/) and it'll load that instead!