Homepage
Default type = mphoto as set in Basic settings -> Photos -> II -> Item 1: Single image type
The subtext is wrapped in a div with the following attribute:
class=”wppa-smx-subtext”
[photo 78598 subtext=”This is subtext from the shortcode<br>Simple html is allowed”]

This is a yucca in our garden
This is subtext from the shortcode
Simple html is allowed
Simple html is allowed
Recommended:
[photo 78598 type=”photo” subtext=”This is subtext from the shortcode<br><i>Simple html is allowed</i>”]

This is subtext from the shortcode
Simple html is allowed
Simple html is allowed
[photo 78598 type=”xphoto” subtext=”This is subtext from the shortcode<br>Simple html is allowed”]
This is a yucca in our garden
You must login to enter a comment
This is subtext from the shortcode
Simple html is allowed
Simple html is allowed
Does not work here:
[photo 78598 type=”slphoto” subtext=”This is subtext from the shortcode<br>Simple html is allowed”]