i added this when i saw your post, here it is at footer ---
https://tiaremarket.com
I downloaded stripe icons and edited one of them to height of 30px (width is relative). File: powered_by_stripe.png (used Photoshop CC)
I used ftp to upload this to .../wp-content/themes/davinci/img/css/powered_by_stripe.png
Then I added this code to the css file (I had to create two css entries based on what is used by the theme -- "partner1" and "p-stripe")
.partner1{display:inline-block;width:132px;height:30px;background:url(./img/css/powered_by_stripe.png) no-repeat}.p-stripe{background-position:0px 0}
Then I edited the footer.php file and look for ----> <li><span><?php _e( 'Payment Methods:', 'ami3' ) ?></span>
Under there - the last icon is: <li><i class="partner p-ae"></i></li> (for Amex)
I added my new code for my stripe icon: <li><i class="partner1 p-stripe"></i></li>
ftp this back to host - DONE