Hi!
You have a display: none; css declaration in .woocommerce-tabs a css attribute, that is why the images is hidden:
.woocommerce-tabs a {
padding: 7px 20px;
float: left;
font-size: 12px;
font-family: Lato,serif;
text-align: center;
text-transform: uppercase;
text-decoration: none;
color: #999;
margin-right: 2px;
margin-bottom: -1px;
display: none;
}You should eliminate this, or overwrite it with another css attribute (you may use !important css declaration for this purpose).
You can get more information about it from your site designer or theme developer (if this css attribute is in your theme).
I will send you screenshots about the css settings via e-mail.
I hope you can solve this behavior according to this information.
Peter