On three separate pages, I had to display products using shortcodes. To customize the size of the images, I utilized Chrome developer tools (option + cmd + i) on my Mac to identify and modify the necessary classes.
.page-id-339 .woocommerce ul.products li.product,
.page-id-339 .woocommerce-page ul.products li.product
{
width: 100%!important;
}
.page-id-3300 .woocommerce ul.products li.product,
.page-id-3300 .woocommerce-page ul.products li.product
{
width: 100%!important;
}
.page-id-16 .woocommerce ul.products li.product,
.page-id-16 .woocommerce-page ul.products li.product
{
width: 100%!important;
}
The trick was using the post id for each page to specifically target and adjust the image sizes of the products displayed. If needed, you could potentially simplify this by removing the post id and targeting all product images with the remaining CSS selector classes.
.woocommerce ul.products li.product,
.woocommerce-page ul.products li.product
{
width: 100%!important;
}
Be sure to include !important in your styling declarations.