pewc_filter_field_image_size.php

<?php
/**
 * Use a different size for add-on images
 */
function prefix_field_image_size( $size ) {
	return 'large';
}
add_filter( 'pewc_filter_field_image_size', 'prefix_field_image_size', 10 );

/**
 * Use a different size for image swatch images
 */
function prefix_image_swatch_thumbnail_size( $size, $item ) {
	return 'large';
}
add_filter( 'pewc_image_swatch_thumbnail_size', 'prefix_image_swatch_thumbnail_size', 10, 2 );