photo reply

 photo reply  is a reply with a photo, thus also a photo post that is in-reply-to another post.

Ryan Barrett
on WordPress:
 * https://snarfed.org/2015-06-01_kyle-mahan-that-thing-where-youre-lecturing-family-members
 * https://snarfed.org/2014-11-11_kyle-mahan-on-twitter-courtarro-i-was-more-going-for-the-meaningless-comparisons-are-meaningless-angle

Kevin Marks
using Known since 2017-12-22:
 * http://known.kevinmarks.com/2017/diso-is-back-im-wearing-my-social-graph-foo-camp
 * shows up as a photo comment on: https://www.monkinetic.blog/diso-after-10-years.html

gRegor Morrill
on gregorlove.com since 2016-02-10:
 * https://gregorlove.com/2016/02/feelin-hot-hot-hot/
 * in-reply-to a tweet
 * https://gregorlove.com/2017/12/han-shrug/
 * in-reply-to an IndieWeb note

Aaron Parecki
on aaronparecki.com since 2018-08-02 (at least, may be earlier examples)
 * https://aaronparecki.com/2018/08/02/10/barriers
 * in-reply-to an IndieWeb note

Marty McGuire
on martymcgui.re since 2018-04-14
 * https://martymcgui.re/2018/04/14/145815/
 * in-reply-to an IndieWeb note
 * posted from Kapowski, a GIF reply Micropub client

Twitter
Since @-replies have their own page level permalinks, Twitter can be considered to support photo replies, e.g.
 * https://twitter.com/schnarfed/status/532281408958775297

Multi-photo reply
Similar to multi-photo posts, there are some sites that support posting multi-photo replies in response to other posts.

Silo multi-photo reply

 * Twitter supports posting an @-reply with up to four photos on it, e.g.
 * https://twitter.com/RonaldVermeij/status/1084159846797246465

No known IndieWeb Examples of multi-photo replies (yet).

When a multi-photo reply is displayed among the comments on the original post, it is a multi-photo comment (more there).