Is it possible to set a limit of one product choice per Category?

Is there a way to select only one product in each product category?

We sell 2 products, but would love to show an image of the purchasable upgrade for the products.

Unfortunately, that's not possible. However, you can use basic fields to list your items/products to achieve this.

For example, you can use the image choices widget to list the items: https://www.jotform.com/widgets/image-choices and then use the section collapse field for the categories: https://www.jotform.com/help/297-show-or-hide-multiple-fields-at-once-using-the-section-collapse-field

Please check and let us know if that could work as an alternative.