When configuring group policy to allow certain icons to appear within Control panel on clients, you need to type the applet code name and not the actual name. For example, for sound and audio to appear within control panel you would type mmsys.cpl. See below for a few more:

Regional and Language Settings (intl.cpl)
Sounds and Audio Devices (mmsys.cpl)
Speech (Sapi.cpl)
System (Sysdm.cpl)
User Accounts (nusrmgr.cpl)
Bluetooth Devices (bthprops.cpl)
Printers and Faxes (control printers)
Power Options (powercfg.cpl)
Phone and Modem Options (telephon.cpl)
Network Connections (ncpa.cpl)
Mouse (control mouse)
Mail (mlcfg32.cpl)
Keyboard (control keyboard)
Internet Options (inetcpl.cpl)
Fonts (control fonts)
Folder Options (control folders)
Display (control desktop)
Automatic Updates (wuaucpl.cpl)
Date and Time (timedate.cpl)
Administrative Tools (control admintools)
Add or Remove Programs (appwiz.cpl)
Add New Hardware (hdwwiz.cpl)
Accessibility Options (Access.cpl)