Hello,
The easiest way to do this is to add the HTML image tag directly in the WooCommerce settings for the BACS title. The Direct Bank Transfer payment method is also known as BACS. Go to WooCommerce –> Settings –> Checkout tab. Click BACS. On this BACS settings page, the Title field should say something like “Direct bank transfer”. Add your image element into the Title field, after “Direct bank transfer”.
For example, change “Direct bank transfer” to:
Direct bank transfer <img src="URL_OF_YOUR_IMAGE" alt="bank transfer icon">
Or you may try to add the image by additional customization using PHP functions and WooCommerce filters if you have PHP skills.
Regards