{% if product.imagesByType('thumbnail') is not empty %}
    {% set path = product.imagesByType('thumbnail').first.path|imagine_filter(filter|default('sylius_shop_product_thumbnail')) %}
{% elseif product.images.first %}
    {% set path = product.images.first.path|imagine_filter(filter|default('sylius_shop_product_thumbnail')) %}
{% else %}
    {% set path = '//placehold.it/200x200' %}
{% endif %}

<img src="{{ path }}" alt="" class="ui bordered image" />

{% if product.imagesByType('thumbnail') is not empty %}
    {% set path = product.imagesByType('thumbnail').first.path|imagine_filter(filter|default('sylius_shop_product_thumbnail')) %}
{% elseif product.images.first %}
    {% set path = product.images.first.path|imagine_filter(filter|default('sylius_shop_product_thumbnail')) %}
{% else %}
    {% set path = '//placehold.it/200x200' %}
{% endif %}

<img src="{{ path }}" alt="{{ product.name }}" class="ui bordered image" />

Add alt attribute to main product image
Add alt attribute to main product image
