How to create menu spread over four lines including images

So, In your place I would go for Dynamic Sidebars because of the control over Widgets is much more easily achieved. But if you still want use WordPress Navigation Menus to do it, to control the output the way you want you need to extend the Class Walker_Nav_Menu, take a look at a usage for the Walker extended.

But I would highly recommend you to go with the Widgets, the API have much more options.