Free WordPress Menu Image pluginFree
Adds a field to load the image in a menu item and displays the image inside the link in the menu before the text.
Now you can upload the second image and set to the mouse over/out effect.
And also change position of title or hide title if need.
And… load images via media uploader!
Now WPML compliant!
Author: Alex Davyskiba aka Zviryatko
Source from: WordPress.org