Simply create a media item to the URL of your photo gallery. You can use a variety of services that offer responsive design to display nicely on mobile phones and tablets.
Your own photo gallery:
Photos by hashtag:
www.instagram.com - the URL would be: https://www.instagram.com/explore/tags/yourtaghere/
- For example: https://www.instagram.com/explore/tags/ashg15/
- Google (search by hashtag, select "images" and apply additional filters as need, then copy the URL)
- http://picsho.com/ - not real time, but moderated feed