The GUI appearance of GiD can be configured to "Classic GiD" This option can be set from Utilities->Preferences and selecting Graphical->Apparence>Appearance->Theme branch.
After restarting GiD, the GUI will appear as follow: 
There is a new theme called 'GiD White Vectorial' that is more recommendable than the 'GiD Classic', because has SVG scalable vector graphics icons, with a more modern look,
