For each image in a library, you can generate thumbnails with different sizes and then choose which size to display on the website.

Following the next steps to configure the image thumbnail sizes:

1. In the main menu, click Administration » Settings in the Basic settings page.

2. Click Thumbnails.

3. To create a new thumbnail size, click Add image thumbnail size.

4. Enter the information and click Done.

SmarterCommerce in last versions used 120x120px

Thumbnail sizes recommended and created in Ecommerce CMS Sitefinity:

SmarterCommerceThumbnail 120x120

SmarterCommerce 40x40

SmarterCommerceCarousel 80x80

SmarterCommerceProductContent 500x500

More information: https://www.progress.com/documentation/sitefinity-cms/thumbnails