A sample image must physically be selected and put in place. As long as there is one image in a set, no matter how large, a sample image can be set, but it must be manually done; the site doesn't do that automatically.
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.