At the moment, the best way of securing a sale is to be visible from the search page. This means designing artwork bigger than you would normally do and also using heavier fonts so that the text can be seen clearly when scrolling through shirts.
If there were larger thumbnails (maybe a choice of three) available this would help both content creators and Amazon.
1. Designers could then use more subtle designs and still have a chance to be seen.
2. Less returns. I've seen a full 15x18 design on a shirt and to be honest, it looked terrible. Text running from armpit to armpit may look good on a flat shirt thumbnail but doesn't look good when worn.
3. Less ink usage. Ink is expensive, and smelly.
4. Please tier me up. I'm due.