What graphics formats does Glade support?
If you are creating a GTK+ application, your graphics must be in XPM format. (GTK+ 2.0 will include the gdk-pixbuf library and so will support many more graphics formats.) If you are creating a GNOME application, most graphics formats can be used. Though the PNG format is preferred for most graphics such as icons. You can convert images between formats using the GIMP graphics application or the ‘convert’ utility in the ImageMagick toolkit.