|| An excellent method for helmets is to obtain empty aluminum cans of various heights for this purpose, such as coffee cans with lids. Stake style display stands made of Acrylic or sealed wood are also commonly used. Once the can is cleaned, it is sprayed with a dark stone-speckle paint to make it more visually appealing. One of the great advantages to this method, are that the liner receives adequate ventilation and no stress is placed upon the old and fragile threads that hold the liner in place.
NOTE: Coffee can supports that have been painted could have acidic trace elements, but I have not seen any damaging effects in the many years I have used them.
Below is an empty coffee can with plastic lids on both ends, next to a helmet for comparison. The plastic lids protect both the inside of the helmet as well as the shelf on which it is displayed from being damaged.