We changed one image and the account grew 24%. I know how that sounds. Here is the actual mechanism, because it is not a hack.
The cheapest test in your account
The main image is the only asset that competes on the search page. Everything else on your listing only gets seen after you win the click. Most brands treat it as a compliance checkbox — white background, product centered, done. That's why it's the cheapest test in your account.
Correct, but invisible at scale
A tools brand we work with had a clean, correct main image of their product on white. Their click-through rate sat below category average and their conversion was strong. That combination is a screaming signal: people who arrive buy, people scrolling past do not stop.
The problem was scale. On a phone, in a grid of 40 results, you could not tell what size the thing was or what it was for. We shot the same product at an angle that implied the use case and made the product fill more of the frame, staying inside Amazon's rules.
CTR went up 38%. Same traffic, same bids, more clicks, and because conversion was already good, revenue followed. Account up 24% in six weeks.
The diagnostic
Pull your CTR and your conversion rate side by side.
Low CTR, high conversion means fix the main image. High CTR, low conversion means the image is overselling and the listing or the price is losing them. Low both means you have a positioning problem, not a photo problem.
Most brands A/B test their headlines and never test the one asset that decides whether anyone reads the headline.