Something is not quite right here: [mclasen@localhost tests]$ file /usr/share/icons/hicolor/48x48/apps/firefox.png /usr/share/icons/hicolor/48x48/apps/firefox.png: PNG image data, 152 x 152, 8-bit/color RGBA, non-interlaced If we cannot install a correctly sized icon for trademark reasons, it would be better to put it in /usr/share/pixmaps. As things currently are, GTK+ operates based on the nominal size, so if you ask for the firefox icon at size 24, you get an icon of size 152 * (24/48) = 76
Fully reproducable here -- for example in the dialog where association is selected Firefox icon looks horribly (being twice the size of others).
fixed in firefox-3.0-0.beta2.10