This code snippet changes the job's company logo size in the JobBoardWP plugin.

jb_post_thumbnail_size.php

<?php

/**
 * Change the job's company logo size. Get rid of the cropped square logo. Use true logo image ratio.
 * Add this code to the file functions.php in the active theme directory.
 */

/**
 * Change the company logo size.
 *
 * @param  string|int[] $size    Requested image size. Can be any registered image size name, or
 *                               an array of width and height values in pixels (in that order).
 * @param  int          $post_id The post ID.
 * @return string
 */
function jb_post_thumbnail_size( $size, $post_id ) {
	$post_type = get_post_type( $post_id );
	if ( 'jb-job' === $post_type && 'thumbnail' === $size ) {

		/**
		 * Available size names: 'thumbnail', 'medium', 'large', 'origin'.
		 * Default size name: 'thumbnail'.
		 * Recommended size name: 'medium'.
		 */
		$size = 'medium';
	}
	return $size;
}

// Change the company logo on the Jobs page.
add_filter( 'jb_get_jobs_query_args', function( $query_args ) {
	add_filter( 'post_thumbnail_size', 'jb_post_thumbnail_size', 10, 2 );
	return $query_args;
} );

// Change the company logo on the single Job page.
add_action( 'jb_before_job_content', function ( $post_id ) {
	add_filter( 'post_thumbnail_size', 'jb_post_thumbnail_size', 10, 2 );
} );

// Change the company logo styles.
add_action( 'wp_footer', function() {
	?>
	<style type="text/css">
		.jb-jobs .jb-jobs-wrapper .jb-job-list-row .jb-job-logo div.jb-job-company-logo-wrapper,
		.jb .jb-job-company .jb-job-company-info .jb-job-logo div.jb-job-company-logo-wrapper {
			height: auto;
			overflow: visible;
		}
	</style>
	<?php
} );

/**
 * Documentation: https://docs.jobboardwp.com/
 * Support forum: https://wordpress.org/support/plugin/jobboardwp/
 */

Example: