Just reading
The New York Times article about how Walt Disney and other animation artists screened their films without dialog, and then
added as little dialog as possible to make sense of the images. The writer says recent animated films have been too talky.
I don't think the image is somehow superior to the soundtrack, as some film purists do. But I do believe that in film, anything you say you should say once. If the image is already saying it, there is no need to say it with dialog. (Which reminds me of the BBC's handbook for writing for radio,
Put Down That Revolver That You're Pointing At Me.)
In TV, it's less clear cut. TV used to be "radio with pictures." You can listen to
The Honeymooners with the picture off and you won't miss much. Probably not a good idea to do that with
The Sopranos, though. The climax of a
Grey's Anatomy is often close to wordless, with doctors hunched over their patients. These days TV aspires to be as cinematic as film.
Ideally both soundtrack and image add something unique. Everything should add something unique; nothing should double up. That's how you get a rich show.
But you can still use Walt's trick
as a tool to stretch your imagination. Remove your voice over and see how the show plays. Remove the snappy dialog and see if you can say some of the same things with images. (See the quasi-dialog-less Buffy episode, "Hush.")
It's risky to do it in a spec. Dialog reads easier than action. Some readers tend to ignore the action, especially if there's dialog to keep the story going. Better to risk that sort of thing in a free lance episode, where you can warn your story editor in advance what you're trying. And certainly, try it in a staff episode, if you've still got time to think...