Collect what you like.
If you have the collector’s passion for finding and learning about your collectibles, you will, at some point, find yourself attracted to items that don’t fit exactly within the main theme of your collection. I am a “scooper” but enjoy many other items associated with the ice cream and soda fountain industry. Straw holders, molds, containers, freezers, dishes, advertising, ephemera, etc, are all great collectibles.
I expect that most of us are somewhat limited by display space and budgets. So how do we decide which items to preserve and which items to only casually give attention to? Would you like to be so intense about one category that you develop certain expertise? The gratification associated with being a semi-expert can be satisfying in itself. Do you only want to learn about ice cream collectibles and appreciate the variety of specialty items that have supported the industry? After all, we can’t take them with us.
I believe that the answer is that there are no rules. Collecting ice cream memorabilia is our pastime and should be as structured or unstructured as our current mood dictates.
Have fun! Include your friends, share your passions, enjoy your hobby, and collect what you like.