APEX: Custom Image on Button Bug

When you use a custom template for your APEX application and you want to use an image on a button, you might encounter a small, trivial bug. Thanks to Anthony Rayner and twitter for a simple workaround. The Setting

For the custom theme that is used in the application that I'm working on, an Application Level Substitution string was created. You can define these substitution strings at the application level, available from the application home page.