You have the option to add an image of a Product in the Settings > Pricing > Products and Services section of ShootQ. This is by no means a requirement, so if you do not want to have an image displayed for an Add On item, you can simply not add one. You can also change or remove an image from the product configuration page as well.
If no image is attached to Product that is designated as an Add On item, it will appear like this in the Proposal or Public Pricing Page:
And this is what it will look like if you do add thumbnails to your products.