clickable image above right of menu

There a couple ways you could do it. You could add a blank menu item and then have add an ID/Class to it in your WP admin. Once you do that then you can create your css to have that ID/Class show an image.

The other way, is to add a text widget in the header widget area, and then add some css to have your widgets float to the right or left so that they align next to each other.