Can I link an external dynamic image to a page created in Visual Composer?
You can use an HTML view that calls the URL you are interested in. The only input parameter of that HTML view is the URL itself. To pull in context-based content to the URL (in which the URL is determined dynamically according to a selection event in another page component), you can create a computed field with a CALC dynamic expression) and map it to the URL field of the HTML view.