Another way to make an image gallery is to use JAlbum. You can create a nice gallery offline (with reduced image size) and then upload the whole album-folder (with all subfolders) by zipping it.
If you want to bulk upload files (not directories) you can also use moodle flashupload.
Resource types
What is the best way to manage photos in Moodle?
Ova je rasprava zaključana, pa više nije moguće odgovoriti na nju.