CT, you might want to check with the manufacturer of your wall mount bracket to see if they have an add-on shelf for it.
If they don't have anything like that (or if they want to steer you to a whole new bracket system with a shelf), you could add on something like this - pretty simple and fairly inexpensive: [ame]http://www.amazon.com/Mount-Bracket-Receiver-Cable-Holder/dp/B000X3KOD2/ref=pd_sim_e_3[/ame]
Bill
