No, 48x48 is not necessary. Statically link to the icon in desktop

src/pam_panic_config/applications/pampanic-config.desktop

@@ -18,7 +18,7 @@ Keywords[es]=PAM;seguridad;contraseña;autenticación;usb;
 Keywords[jp]=PAM;セキュリティ;パスワード;認証;USB;
 Exec=sudo pam_panic_config
 TryExec=pam_panic_config
-Icon=pampanic
+Icon=/usr/share/icons/hicolor/scalable/apps/pampanic.svg
 Terminal=true
 Categories=Settings;Security;ConsoleOnly;
 StartupNotify=false