[Anders Broman <a.broman@xxxxxxxxxxxx>]

Hi,
Googling it looks like we'd want to do something along these lines instead:

GList *Main_Icon_List=NULL;
GdkPixbuf *Icon;

 icon = gdk_pixbuf_new_from_xpm_data ((const char **) wsicon16_xpm);
Main_Icon_List = g_list_append (Main_Icon_List, Icon);
gtk_window_set_icon_list(GTK_WINDOW(Window), Main_Icon_List);

"Recommended sizes to provide: 16x16, 32x32, 48x48 at minimum, and 
larger images (64x64, 128x128) if you have them."

Unfortunately I don't have a Linux system to try it out on at the 
moment, so I'd appreciate if some one that has could
try it out.

Best regards
Anders