An img element must have an alt attribute, except under certain conditions.

Can I add a vote for this as well? This widget is great but it must validate!

Actually, I figured out how to do it in library/enjoyinstagram_shortcode.php:

$shortcode_content .= "<div class=\"box\"><a title=\"{$entry->caption->text}\" rel=\"gallery_swypebox\" class=\"swipebox\" href=\"{$entry->images->standard_resolution->url}\"><img src=\"{$entry->images->standard_resolution->url}\" alt=\"{$entry->caption->text}\"></a></div>";

Worked great for me!

Looking forward to being able to add Alt Images also. I actually prefer not to access pho code if not necessary.