It just makes it harder to find machines with good decals in that area. People have always modified their tools to suit their needs. It was an honest use of the machine at the time though most of us here wouldn't do it now. Besides, modern machines won't let you.
Roserips told me that Elk leather will stop a needle. We were talking about me making a leather thimble at the time. Leather would be a good backing if you want a pin cushion there. A thick piece of leather would be flexible and stop the pins from hitting the machine surface. We don't jab a pin cushion with the same force we use on a thimble. A stiff but still flexible piece of plastic might work as a backing too if you want a functional pincushion there that won't further damage your machine's finish.
Rodney