If you change the folder location of the Gallery so your photos are stored somewhere else, just leave all the Gallery folders in the original location also so these links remain working.
I changed my folder location thinking I was just changing where the photos were stored, but found out after in fact I was changing where EVERYTHING needed to be. I still don't like the fact all the images and thumbnails are stored in the main Gallery folder along with a bunch of other folders and source files.
Original uploaded images should be in their own folder, and thumbnails in another folder on their own.