"Select linked" images amongst shaders in Outliner

I'm basically trying to clean up my project to send it to a render farm. The most important is to remove texture links that I don't really need anymore. However in big projects with lots of shaders there is no way to see which image is used in which shader. In the blender file view of the outliner, clicking on "Select linked" has no effect, I wish it would select the shaders in which they are used so that I can see if a specific image is really important or not.