The main website http://qcu.be doesn't show the favicon. Interestingly the trac at http://trac.qcu.be does show it. Even when shown, the current icon could be improved by removing the word "cubed" from below the Q sign and accordingly enlarging the Q sign itself. If these icons allow for transparency, it would be good to make the whites transparent.
Then it should also be used for the main site.

-Vartan