Usability research has shown us time and again that icon-only methods of navigation frustrate people. The designer is trying to be space efficient or clever, but users find these schemes hard to comprehend and memorize. Especially for abstract concepts, images rarely work well for helping users navigate an interface.
Menus designed without clear, text-based information are what Vincent Flanders of Web Pages That Suck refers to as “mystery meat navigation”.
Make your menu items and other elements of navigation unmistakable. When in doubt, use text.
Mystery Meat Navigation: An Introduction by Vincent Flanders