In reply to:
Unfortunately everything would fall off of it.
Actually, I keep a decorative (but functional) African drum on top of my subwoofer. It hasn't fallen off yet. My wife used to keep a houseplant on top of the sub, but we discovered that the plant kept leaning over to the side after a while. Turns out the bass would vibrate the soil so much that the roots would loosen and the plant would fall over.
I was happy about the plant's relocation. Now there's a much smaller chance of having a water spilling accident on my sub.
