Displaying the tabs with icons and text is something that can be configured in the extension preferences and is actually the default:

http://share.chrispederick.com/dT5uxy/6f2HnGob

Older versions of the extension are available here, but note that they are not supported and will not work in future versions of Firefox:

https://addons.mozilla.org/en-US/firefox/addon/web-developer/versions/