This article from econsultancy discusses three case studies that measured the impact with image size on the landing pages on the conversion ratio. What is the outcome? In all three cases, using a bigger image boosted the conversion ratio of the page

  1. Boosting the product image by 28% lead to a 63% improvement in click through rate
  2. Increasing the size of the call-to-action button more than doubled the click through rate
  3. Having a bigger background image boosted the click through rate by 36%

Some of these findings are directly applicable to smallbusiness ecommerce websites. Please read the article for more details.