Menu with images

I had this same problem, a client wanted image-only buttons in the nav.

The solution I found was based on this article. So basically:
1. Add a custom menu.
2. Add a custom link.
3. In the Label, put the url of the image that will represent the ‘button’ for that page.
4. In the URL, add the url of the page where the user will be taken on click.

A little bit longer, but for me it was what I needed.