hmmm, I still have one problem.
For unregistered users, the Image Gallery shows up empty, but once I log in it works fine.
I checked my gallery and unregistered users can view thumbnails and previews just fine. I checked my module/gallery permissions and all of them are set correctly.
Any help on this would be appreciated.
Edit:
I did more digging and logged on as another user. Apparently, the thumbnails show up only when I have a user assigned to a user group:
For those who are not assigned to any groups or for unregistered users, no thumbnails show.