If you’re concerned about SEO, writing good alt and title text can help, but if you don’t want them at all you can remove them using a custom slideshow template.
Because the_post_thumbnail
function for the slide images loads the whole image tag, you can’t edit it. But you can make your own image tag without an alt or title tag using the URL of the slide image.
Here is the code you need to do this. This replaces everything within the “mslide” div container which starts on line 103:
<?php // Get just the URL for the slide featured image
$featuredslide = wp_get_attachment_image_src( get_post_thumbnail_id($GLOBALS['post']->ID), 'featured-slide' ); ?>
<?php // Adds slide image with Slide URL link
if ( get_post_meta( $post->ID, "slide_url_value", $single = true ) != "" ): ?>
<a href="<?php echo get_post_meta( $post->ID, "slide_url_value", $single = true ); ?>"><img src="<?php echo esc_attr($featuredslide[0]); ?>" alt="" /></a>
<?php // Adds slide image without Slide URL link
else: ?>
<img src="<?php echo esc_attr($featuredslide[0]); ?>" alt="" />
<?php endif; ?>