I figure out how to show attribute in category of product list, what I need is to display an image instead of text.
Eg. I have an attribute text ASUS and a image located in media/brands/ named asus.gif or instead of Western-Digital display image located in media/brands/western-digital.gif.
I hope you understand
If your attribute is a dropdown one you could add a new column in the table eav_attribute_option_value and in the "manage options/labels" tab of the manage attribute page in the admin panel. For each option values, next to each store traduction, you could store the name of your image and retrieve it in your templates.. it require some development but it's doable and easy to administrate.
Or the quick and dirty way : use the admin label string, lowercase it and clean to retrieve an image related filename