Hello Guido,
Hm, unfortunately this cannot be turned off right now but you can always customize it by editing the theme file /components/com_easysocial/themes/wireframe/photos/item.php
<a data-photo-image-link
href="<?php echo $photo->getPermalink();?>"
title="<?php echo $this->html( 'string.escape' , $photo->title ); ?>">
<?php
// These images are hidden from user.
// It allows us to switch between thumbnail/featured and SEO crawling.
?>
<i data-photo-image-thumbnail
data-src="<?php echo $photo->getSource( 'thumbnail' ); ?>"></i>
<i data-photo-image-featured
data-src="<?php echo $photo->getSource( 'featured' ); ?>"></i>
<i data-photo-image-large
data-src="<?php echo $photo->getSource( 'large' ); ?>"></i>
</a>
However, I really reckon that you keep the photo title otherwise there's no where the user can view the title of the photo