Comment 2 for bug 294547

I spoke with Ted Gould today and he said this was because Pidgin doesn't follow the Freedesktop.org Icon Naming Spec: http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html

Pidgin needs to rename the icons it installs to match the names in the icon-naming-spec. Then, it should use gtk_icon_theme_append_search_path() to append its directory to the end of the path (on GTK+ 2.4 and above) to provide the default icons if the user's theme doesn't define them. Then icons should be loaded with gtk_icon_theme_lookup_icon() on GTK+ 2.4 and above. (The fallback code can just load the icons from Pidgin's own directory.)

On the Ubuntu side, once that is done, we'll want to ensure that the Human theme ships the nice Pidgin icons. ;)