For the SCSocialStream module, you can find where we're adding the images in the /media/sourcecoast/themes/scsocialstream/default/facebook.php file. There are 4 instances of the img tags. Could you try adding an alt attribute like the following to see if that helps resolve your issue:
Line 19:
echo '<img src="' . JUri::root(true) . '/media/sourcecoast/images/provider/facebook/icon.png" alt="Facebook Login" />';
Line 25:
<div class="author-image"><img src="'.JFBCFactory::provider('facebook')->profile->getAvatarUrl($this->authorID,false,null).'" alt="Author"/></div>
Line 58:
echo '<div class="image"><img src="' . $this->thumbPicture . '" alt="Post Thumbnail"/></div>';
Line 81:
<span class="from text-left"><img src="https://graph.facebook.com/' . $comment['from']['id'] . '/picture" width="25" alt="Comment Thumbnail"/> ' . $comment['from']['name'] . '</span>
Of course if you're referring to something other than the SCSocialStream module please provide more details/a specific URL where I can see the tags. Let me know if that helps and I can easily check this in for the next release.
-Melissa
Alt tag for Facebook stream
