Replace Newsletter sign-up button with an image

Site URL: https://caper-badger-3s6d.squarespace.com/news

How do I replace my newsletter ''join'' button, with a custommade icon (image)? I want it to be the same height size as the newsletter-form-field-element.

 Can anyone help me?

Add to Design > Custom CSS

/* Join button */
.newsletter-block .newsletter-form-button-wrapper * {
    background: transparent !important;
    color: transparent !important;
}
.newsletter-block .newsletter-form-button-wrapper {
    background-image: url(https://cdn.pixabay.com/photo/2020/12/19/03/27/person-5843476__340.jpg);
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center center;
}

Thank you @tuanphan!