Yes, awareness of correct mouth positions is the foundation of proper pronunciation, and visuals are an important part of that. But don't just throw down some cutaway views from the anatomy textbook and expect students to get it. No one imagines that's how the inside of their mouth looks. Use simple line drawings, exaggerating only the relevant parts used in the production of each sound, and use gestures and mirrors to ground the images in the physical stuff.
I do have a complete method for teaching and learning English pronunciation that ties mouth positions, phonics, and spelling into one comprehensive system that is easy and effective to use because it is grounded in the learner's experience. If you are interested in learning how to teach it or use it, even just the parts that you particularly need, please contact me here.
In the meantime, please enjoy this silly little meme...