I just have mine on the shelf. Though it's a fireproof safe, so the shelf stuff is a molded plastic-like material. I'm not sure if I would want to leave them right on a metal shelf for fear of scratching.
As for laying them on a silicon cloth, I don't think that would be a good idea as it would collect any oil from the gun or moisture within the safe.
To control moisture, I have a silicon pack that came with the safe, along with one I bought at the store.
Figure when not recently shot, I'll go in and wipe them down with a silicone cloth every few weeks, and that should keep them in good condition.