Hi,
The option is not available to display photo gallery by category in this default pretty photo gallery script.
Please use NextGEN gallery plugin to display categorized image gallery.
The image http://staging.bandrecordingslive.com/wp-content/uploads/2019/06/20190615_214429.jpg is very high resolution of size 4032 × 2268 pixels that’s why it is looking very tiny on mobile device. Please use small/medium size of images for photo gallery.
Regards
Grace Themes