Ideally, there should be two options in category and search result view:
1. Site default: If front image exists, display front image. If front does not exist, show cart_art image. If front image does not exist and cart image does note exist, show No Art
2. User preference: Use Site default or choose priority. Then a user can choose to always show cart_art image as the default. Possibility exists to have this done by category type (hardware, games, accessory)
Currently the site default is to show the Front art, no matter what. There is no user preference.
Regarding these items specifically, Arduboy front image should be how it is sealed. So it would look like this with the "Nutrition Facts" label being the front, and the bare side as being the back:
https://www.ebay.com/itm/332996395467Art Master is a pack-in cartridge. It is allowed to have the cartridge picture be the front art on its entry.
For example, pack-in cartridges from consoles are like this, such as this Vectorman 2:
https://vgcollect.com/item/133047Or even this example of Lethal Enforcers pack-in from the accessory
https://vgcollect.com/item/138745Which becomes a weird situation since the community voted on Accessories with games to be in the games category, and (FYI) it technically is not considered to be a dupe of this
https://vgcollect.com/item/84042