Recently investigated the use of images rather than text for links in menu items on WordPress pages. Pleased to report that not only is it possible, it is actually very easy, and with the breadth of information out there in the WordPress community, well documented. Here is the process:

• Upload the image thumbnails into your Media area.
• Install and activate the Menu Image plugin
• With the plugin activated – visit the Appearance : Menus page
  • Select the menu items
  • Click the Custom Link item top right to expand.

Select Image, approximate thumbnail size, (I find 36×36 reasonable for menus) then, if you only want the image and no text, set Title position to Hide.