How handle large number of images in gallery node Drupal 7
I do not know the intended site behaviour, or interface, for your galleries.  However, I would restructure the site.  Have you looked at each gallery "entry" being a node with 1 picture field and 1 taxonomy term reference?  The terms would then be your "galleries", you could use views to build the pages any way you want, even lazy load.  You could add sorting, and since you would not have 100+ field entries on any one entity, loading the entity into a variable for the various page build tasks would be far faster.  Gallery nodes work fine if they have less than 30 entries, but it sounds like your data management could use some revision.